Fibrous sheet

ABSTRACT

Provided are a fibrous sheet having a stress relaxation rate defined by the following formula of less than or equal to 85%: 
       stress relaxation rate [%]=(stress  S   5  at extension after five minutes/stress  S   0  at initial extension)×100
 
     when a stress at extension immediately after extension in an in-plane first direction at 50% elongation is defined as a stress S 0  (N/50 mm) at initial extension, and a stress at extension at a time of extending in the first direction at 50% elongation for five minutes is defined as a stress S 5  (N/50 mm) at extension after five minutes, and a bandage including the fibrous sheet.

TECHNICAL FIELD

The present invention relates to a fibrous sheet suitably usable as abandage or the like.

BACKGROUND ART

A bandage is used not only to directly protect an application site suchas an affected part by being wrapped around the application site, or tofix another protective member (such as a gauze) to the application site,but also, when the bandage has stretchability, to stop bleeding of awound site by a compression force using its stretchability at the timeof wrapping and to improve swelling by promoting a blood flow. In recentyears, a bandage has been applied to compression therapy where treatmentis carried out by compressing an affected part, such as treatment andimprovement of lower extremity varicose veins.

As a method of imparting stretchability to a bandage, there have beenknown 1) a method of weaving, into a fabric, yarn formed of astretchable material such as an elastomer typified by rubber and 2) amethod of combining a layer formed of a stretchable material such as anelastomer with a nonstretchable fabric or impregnating a nonstretchablefabric with a stretchable material, and many stretchable bandagesproduced by using such methods are commercially available.

For example, Japanese Patent No. 3743966 (PTD 1) discloses a stretchablebandage imparted with stretchability in the longitudinal direction byincluding elastic yarn for warp. Japanese Patent No. 5600119 (PTD 2)discloses an elastic nonwoven fabric fibrous web imparted withstretchability by a method of entangling a nonwoven fabric fiber with anextended elastic filament and then relaxing the extended state of theelastic filament. Japanese National Patent Publication No. 2014-515320(PTD 3) discloses a stretchable self-adherent composite article obtainedby impregnating an elastic composite article that includes a nonwovenfibrous coverweb, a woven scrim, and a plurality of elastic yarnslocated between the coverweb and the woven scrim, with an elastomericpolymeric binder.

CITATION LIST Patent Document PTD 1: Japanese Patent No. 3743966 PTD 2:Japanese Patent No. 5600119 PTD 3: Japanese National Patent PublicationNo. 2014-515320 SUMMARY OF INVENTION Technical Problems

In a conventional stretchable bandage formed by combining elastomermaterials such as a rubber yarn, there have been problems such as bloodcirculation disturbance or a feeling of pain when such a bandage iswrapped around an application site for a long time. Such a problem canbe suppressed by reducing tensile stress of the materials constitutingthe bandage. However, when a bandage with small tensile stress is used,there is a tendency for the bandage to be wrapped around an applicationsite with strong tension in order to firmly fix the bandage to theapplication site, so that this may rather aggravate the above-describedproblem.

When a bandage is applied to a site to be bent and stretched, such as ajoint part, it is certainly advantageous that the bandage hasstretchability in view of increasing the ease of bending (movability) ofthe joint part. However, there has been still room for improvement inthe ease of bending of the joint part, in particular the ease of bendingof small joint parts such as fingers.

A bandage can be applied to every part of the body. Accordingly, whenthe conventional bandage having stretchability is wrapped around a sitehaving surface protrusions and recesses, such as a joint part, thebandage can be wrapped along a surface in the vicinity of the peaks ofthe protrusions and has good adhesion to the surface; however, thewrapped bandage does not satisfactorily follow the surface at itsperiphery (recesses), so that the bandage may float from the surface. Inthis specification, when a sheet such as a bandage is wrapped around asite having surface protrusions and recesses, the property of being ableto be wrapped along the shapes of the surface protrusions and recessesis referred to as a “concavo-convex fitting property”.

When a bandage is inferior in the concavo-convex fitting property,floating of the wrapped bandage may occur as described above, and inthis case, the bandage is apt to become loose and is unwrapped, or adesired compression force cannot be obtained in some cases. When abandage is wrapped with strong tension to follow surface protrusions andrecesses, there occur problems such as blood circulation disturbance ora feeling of pain due to seaming.

A first object of the present invention is to provide an extensiblefibrous sheet capable of suppressing problems such as blood circulationdisturbance and pain even when the fibrous sheet is wrapped around anapplication site for a long time, and a bandage including the fibroussheet.

A second object of the present invention is to provide a fibrous sheetless liable to disturb the bending motion of a site to be bent andstretched, such as a joint part, even when the fibrous sheet is wrappedaround the site, and a bandage including the fibrous sheet.

A third object of the present invention is to provide a fibrous sheethaving a good concavo-convex fitting property and capable of beingwrapped along the shape of surface protrusions and recesses even whenwrapped with moderate strength, and a bandage including the fibroussheet.

Solutions to Problems

In order to achieve the first object, the present invention provides afibrous sheet and a bandage described below.

[1] A fibrous sheet having a stress relaxation rate defined by a formulabelow of less than or equal to 85%:

stress relaxation rate [%]=(stress S ₅ at extension after fiveminutes/stress S ₀ at initial extension)×100

when a stress at extension immediately after extension in an in-planefirst direction at 50% elongation is defined as a stress S₀ (N/50 mm) atinitial extension, and a stress at extension at a time of extending inthe first direction at 50% elongation for five minutes is defined as astress S₅ (N/50 mm) at extension after five minutes.

[2] The fibrous sheet described in [1],

wherein the stress relaxation rate is greater than or equal to 65%.

[3] The fibrous sheet described in [1] or [2],

wherein the stress S₀ at initial extension is from 2 to 30 N/50 mm.

[4] The fibrous sheet described in any one of [1] to [3],

wherein the fibrous sheet has a curved surface sliding stress of 5 to 30N/50 mm.

[5] The fibrous sheet described in any one of [1] to [4],

wherein the fibrous sheet has a length direction and a width direction,and

the first direction is the length direction.

[6] The fibrous sheet described in any one of [1] to [5],

wherein the fibrous sheet is a nonwoven fabric sheet.

[7] The fibrous sheet described in any one of [1] to [6],

wherein the fibrous sheet is a bandage.

In order to achieve the second object, the present invention provides afibrous sheet and a bandage described below.

[8] A fibrous sheet that satisfies a formula below:

{T ₃/(3×T ₁)}×100≤85[%]

when a thickness of a single fibrous sheet measured in accordance with Amethod specified in JIS L 1913 is defined as T₁ [mm], and a thickness ofthree superimposed sheets measured under the same conditions is definedas T₃ [mm].

[9] The fibrous sheet described in [8],

wherein the fibrous sheet satisfies a formula below:

S ₂ /S ₁≥3

when a stress at extension at a time of extension in an in-plane firstdirection at 50% elongation is defined as a stress S₁ (N/50 mm) at 50%extension, and a stress at extension at a time of extension in anin-plane second direction orthogonal to the first direction at 50%elongation is defined as a stress S₂ (N/50 mm) at 50% extension.

[10] The fibrous sheet described in [9],

wherein the fibrous sheet has a length direction and a width direction,and

the first direction is the width direction.

[11] The fibrous sheet described in any one of [8] to [10],

wherein the fibrous sheet has a basis weight of greater than or equal to50 g/m².

[12] The fibrous sheet described in any one of [8] to [11],

wherein the fibrous sheet has a compression elastic modulus measured inaccordance with JIS L 1913 of less than or equal to 85%.

[13] The fibrous sheet described in any one of [8] to [12],

wherein the fibrous sheet has a curved surface sliding stress of 3 to 30N/50 mm.

[14] The fibrous sheet described in any one of [8] to [13],

wherein the fibrous sheet is a nonwoven fabric sheet.

[15] The fibrous sheet described in [14],

wherein the fibrous sheet includes crimped fibers.

[16] The fibrous sheet described in any one of [8] to [15],

wherein the fibrous sheet is a bandage.

In order to achieve the third object, the present invention provides afibrous sheet and a bandage described below.

[17] A fibrous sheet having a length direction and a width direction,

wherein a bending resistance in the width direction measured inaccordance with Handle-o-Meter method specified in JIS L 1913 is lessthan or equal to 300 mN/50 mm.

[18] The fibrous sheet described in [17],

wherein the bending resistance in the width direction is lower than abending resistance in the length direction.

[19] The fibrous sheet described in [17] or [18],

wherein the fibrous sheet has a compression elastic modulus measured inaccordance with JIS L 1913 of less than or equal to 85%.

[20] The fibrous sheet described in any one of [17] to [19],

wherein the fibrous sheet has a curved surface sliding stress of 3 to 30N/50 mm.

[21] The fibrous sheet described in any one of [17] to [20],

wherein the fibrous sheet is a nonwoven fabric sheet. [22] The fibroussheet described in [21],

wherein fibers constituting the nonwoven fabric sheet have an averagefineness of less than or equal to 20 dtex.

[23] The fibrous sheet described in [21] or [22],

wherein the fibrous sheet includes crimped fibers. [24] The fibroussheet described in any one of [17] to [23],

wherein the fibrous sheet is a bandage.

Advantageous Effects of Invention

The present invention can provide an extensible fibrous sheet capable ofsuppressing problems such as blood circulation disturbance and pain evenwhen the fibrous sheet is wrapped around an application site for a longtime, and a bandage including the fibrous sheet.

The present invention can provide a fibrous sheet less liable to disturbthe bending motion of a site to be bent and stretched, such as a jointpart, even when the fibrous sheet is wrapped around the site, and abandage including the fibrous sheet.

The present invention can provide a fibrous sheet having a goodconcavo-convex fitting property and a bandage including the fibroussheet.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram showing a method of preparing a sample formeasuring curved surface sliding stress.

FIG. 2 is a cross-sectional schematic diagram showing the sample formeasuring the curved surface sliding stress.

FIG. 3 is a schematic diagram showing a method of measuring the curvedsurface sliding stress.

DESCRIPTION OF EMBODIMENTS First Embodiment

(1) Characteristics of Fibrous Sheet

A fibrous sheet according to the present embodiment (hereinafter alsosimply referred to as a “fibrous sheet”) is an extensible fibrous sheetcapable of being suitably used not only as a general bandage but also asa medical article such as a compression bandage used for hemostasis,compression therapy, and so on. In the present specification,“extensible/having extensibility” means that a stress at 50% extensionis exhibited in at least one direction (first direction) in the sheetplane, and the stress at 50% extension is preferably greater than orequal to 0.1 N/50 mm, more preferably greater than or equal to 0.5 N/50mm, further preferably greater than or equal to 1 N/50 mm.

The stress at 50% extension means stress at extension immediately afterextension in the first direction at 50% elongation, and in the presentspecification, this stress is also referred to as “stress S₀ at initialextension” [unit: N/50 mm]. The stress S₀ at initial extension ismeasured by a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913. The stress S₀ at initial extensionis preferably less than or equal to 30 N/50 mm, more preferably lessthan or equal to 20 N/50 mm, further preferably less than or equal to 15N/50 mm. The stress S₀ at initial extension being less than or equal to30 N/50 mm is advantageous for suppressing problems such as bloodcirculation disturbance and pain that may occur when the sheet iswrapped around an application site for a long time.

The first direction of the fibrous sheet may be a flow direction (MDdirection) of the fibrous sheet in a production process, and when thefibrous sheet has, for example, a length direction and a width directionlike a bandage, the first direction is preferably the length directionof the fibrous sheet. In this case, the fibrous sheet as a bandage iswrapped around an application site while extending along the lengthdirection thereof. When the fibrous sheet has a length direction and awidth direction, a CD direction orthogonal to the MD direction ispreferably the width direction.

The stress at 50% extension in a direction other than the firstdirection in the fibrous sheet, for example, the CD direction, or awidth direction when the fibrous sheet has a length direction and thewidth direction like a bandage is, for example, 0.5 to 50 N/50 mm, andpreferably 1 to 30 N/50 mm.

When a stress at extension at the time of extending in the firstdirection at 50% elongation for five minutes is defined as a stress S₅(N/50 mm) at extension after five minutes,

a stress relaxation rate defined by the following formula:

Stress relaxation rate [%]=(stress S ₅ at extension after fiveminutes/stress S ₀ at initial extension)×100

is less than or equal to 85%.

The “stress at extension at the time of extending in the first directionat 50% elongation for five minutes” means a stress at extensiongenerated when the sheet is extended in the first direction at 50%elongation and held in this state for five minutes. Similarly to thestress S₀ at initial extension, it is measured by a tensile test in the“Test methods for nonwovens” specified in JIS L 1913.

According to the fibrous sheet having a stress relaxation rate of lessthan or equal to 85%, it is possible to effectively suppress problemssuch as blood circulation disturbance and pain that may occur when thesheet is wrapped around an application site for a long time. That is,according to the fibrous sheet, the tensile stress of the fibrous sheetis moderately relaxed with time as the fibrous sheet is wrapped aroundthe application site, so that the above-described problems caused byseaming are less likely to occur. The stress relaxation rate ispreferably less than or equal to 84%, more preferably less than or equalto 83%.

The stress relaxation rate is preferably greater than or equal to 65%,more preferably greater than or equal to 70%, further preferably greaterthan or equal to 75%. When the stress relaxation rate is within thisrange, it is possible to suppress occurrence of displacement and peelingof the wrapped fibrous sheet due to gradual loosening of the wrappedstate after the fibrous sheet is wrapped around an application site.

The fibrous sheet preferably exhibits self-adhesiveness. In the presentspecification, the “self-adhesiveness” refers to a property allowingfibers on a fibrous sheet surface to engage with each other or come intoclose contact with each other due to superposition (contact) of thefibers and to be hooked or fixed. The fibrous sheet havingself-adhesiveness is advantageous when the fibrous sheet is a bandage orthe like. For example, in the case where the fibrous sheet is a bandage,after the bandage is wrapped around an application site, the wrappedfibrous sheets are pressed against each other while being extended bysuch an operation that an end of the bandage is overlapped on (or tornand then overlapped on) a bandage surface located under the end, so thatthe fibrous sheets are joined and fixed to each other, therebyexpressing self-adhesiveness.

When the fibrous sheet itself has self-adhesiveness, it is unnecessaryto form a layer formed of a self-adhesive agent such as an elastomer ora pressure-sensitive adhesive on a surface of the fibrous sheet or toprepare separately a fastener for fixing the tip after wrapping. It ispreferable that the fibrous sheet is constituted only of a non-elastomermaterial. More specifically, it is preferable that the fibrous sheet isconstituted only of fibers. For example, Japanese Patent Laying-Open No.2005-095381 (PTD 4) describes that an acrylic polymer (claim 1) or alatex (paragraphs [0004] to [0006]) is caused to adhere as aself-adhesive agent to at least one side of a bandage base material.However, when such a layer formed of an elastomer is formed on thefibrous sheet surface, this may cause problems such as blood circulationdisturbance and pain when the sheet is wrapped around an applicationsite for a long time. The layer formed of an elastomer may induce skinirritation and allergy when wrapped around an application site.

The self-adhesiveness of the fibrous sheet can be evaluated by a curvedsurface sliding stress. From the viewpoint of the self-adhesiveness, itis preferable that the fibrous sheet has a curved surface sliding stressof, for example, greater than or equal to 3 N/50 mm, preferably greaterthan or equal to 5 N/50 mm, and the curved surface sliding stress ispreferably higher than breaking strength. Since it is relatively easy tounwrap the wrapped fibrous sheet if desired, the curved surface slidingstress is preferably less than or equal to 30 N/50 mm, more preferablyless than or equal to 25 N/50 mm. The curved surface sliding stress ismeasured using a tensile tester in accordance with the method describedin Examples section (FIGS. 1 to 3).

The fibrous sheet preferably has a hand cut property. In the presentspecification, the “hand cut property” refers to a property enablingbreakage (cutting) by hand tension. The hand cut property of the fibroussheet can be evaluated by breaking strength. From the viewpoint of thehand cut property, the fibrous sheet has a breaking strength in at leastone direction in the sheet plane of preferably 5 to 100 N/50 mm, morepreferably 8 to 60 N/50 mm, further preferably 10 to 40 N/50 mm. Whenthe breaking strength is within the above range, it is possible toimpart a good hand cut property enabling relatively easy breakage(cutting) by hand. If the breaking strength is too large, the hand cutproperty deteriorates, making it difficult to cut the fibrous sheet withone hand, for example. On the other hand, if the breaking strength istoo small, the strength of the fibrous sheet becomes insufficient tocause easy breakage of the fibrous sheet, and durability andhandleability are lowered. The breaking strength is measured by atensile test in accordance with the “Test methods for nonwovens”specified in JIS L 1913.

At least one direction in the sheet plane is a tensile direction whenthe fibrous sheet is cut by hand, and is preferably the above-describedfirst direction. The first direction may be the MD direction, and whenthe fibrous sheet has, for example, a length direction and a widthdirection like a bandage, the first direction is preferably the lengthdirection of the fibrous sheet. That is, when the fibrous sheet is usedas a bandage, it is usual to break the bandage in the length directionafter the bandage is wrapped around an application site while beingextended along the length direction thereof, and therefore the firstdirection is preferably the length direction as the tensile direction.

The breaking strength in a direction other than at least one directionin the sheet plane, for example, the CD direction, or a width directionwhen the fibrous sheet has a length direction and the width directionlike a bandage is, for example, 0.1 to 300 N/50 mm, preferably 0.5 to100 N/50 mm, more preferably 1 to 20 N/50 mm.

From the viewpoint of the hand cut property, it is preferable that thefibrous sheet is constituted only of a non-elastomer material. Morespecifically, it is preferable that the fibrous sheet is constitutedonly of fibers. If a layer formed of an elastomer, etc. is formed on thefibrous sheet surface, the hand cut property may be lowered.

The fibrous sheet has an elongation at break in at least one directionin the sheet plane of, for example, greater than or equal to 50%,preferably greater than or equal to 60%, more preferably greater than orequal to 80%. When the elongation at break is within the above range, itis advantageous for enhancing the stretchability of the fibrous sheet.In the case where the fibrous sheet is used as a bandage, thefollowability can be enhanced when the fibrous sheet is applied to asite with large movement, such as a joint. The elongation at break in atleast one direction in the sheet plane is usually less than or equal to300% and preferably less than or equal to 250%. The elongation at breakis also measured by a tensile test in accordance with the “Test methodsfor nonwovens” specified in JIS L 1913.

At least one direction in the sheet plane is preferably theabove-described first direction. The first direction may be the MDdirection, and when the fibrous sheet has, for example, a lengthdirection and a width direction like a bandage, the first direction ispreferably the length direction of the fibrous sheet.

The elongation at break in a direction other than at least one directionin the sheet plane, for example, the CD direction, or a width directionwhen the fibrous sheet has a length direction and the width directionlike a bandage is, for example, 10 to 500%, preferably 100 to 350%.

The fibrous sheet has a recovery rate after 50% extension in at leastone direction in the sheet plane (recovery rate after 50% extension) ispreferably greater than or equal to 70% (less than or equal to 100%),more preferably greater than or equal to 80%, further preferably greaterthan or equal to 90%. When the recovery rate after 50% extension iswithin the range, the followability to extension is enhanced, and forexample when the sheet is used as a bandage, the bandage satisfactorilyfollows the shape of a portion around which the bandage is wrapped, andat the same time, it is advantageous for improvement of theself-adhesiveness due to friction between the overlapped fibrous sheets.When the extension recovery rate is excessively small, the fibrous sheetcannot follow movement of a portion around which the fibrous sheet iswrapped in the case where the portion has a complex shape or movesduring use of the fibrous sheet, and a portion deformed by body movementdoes not return to its original shape, thus weakening fixation of thewrapped fibrous sheet.

At least one direction in the sheet plane is preferably theabove-described first direction. The first direction may be the MDdirection, and when the fibrous sheet has, for example, a lengthdirection and a width direction like a bandage, the first direction ispreferably the length direction of the fibrous sheet.

The recovery rate after 50% extension is defined by the followingformula:

Recovery rate after 50% extension (%)=100−X

when, in a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913, a residual strain (%) after the testis defined as X when load is removed immediately after the elongationrate reaches 50%.

The recovery rate after 50% extension in a direction other than at leastone direction in the sheet plane, for example, the CD direction, or awidth direction when the fibrous sheet has a length direction and thewidth direction like a bandage is, for example, greater than or equal to70% (less than or equal to 100%), preferably greater than or equal to80%.

The fibrous sheet has a basis weight of preferably 30 to 300 g/m², morepreferably 50 to 200 g/m². The fibrous sheet has a thickness of, forexample, 0.2 to 5 mm, preferably 0.3 to 3 mm, more preferably 0.4 to 2mm. When the basis weight and the thickness are within these ranges, abalance between the stretchability and the flexibility, touch feeling orcushioning property of the fibrous sheet is good. A density (bulkdensity) of the fibrous sheet can be a value corresponding to theabove-described basis weight and thickness, and the density (bulkdensity) is, for example, 0.03 to 0.5 g/cm³, preferably 0.04 to 0.4g/cm³, more preferably 0.05 to 0.2 g/cm³.

The fibrous sheet has an air permeability measured by the Frazier methodof preferably greater than or equal to 0.1 cm³/(cm²·second), morepreferably 1 to 500 cm³/(cm²·second), further preferably 5 to 300cm³/(cm²·second), particularly preferably 10 to 200 cm³/(cm²·second).When the air permeability is within this range, the fibrous sheet ismore suitably used for the human body, such as a bandage, because thefibrous sheet is good in air permeability and is hardly stuffy.

(2) Structure and Production Method of Fibrous Sheet

The fibrous sheet of the present embodiment is not particularly limitedas long as it is constituted of fibers, and the fibrous sheet may be,for example, a woven fabric, a nonwoven fabric, a knit (knitted fabric),or the like. Although the shape of the fibrous sheet can be selectedaccording to use application, it is preferably a rectangular sheet shapehaving a length direction and a width direction such as a tape shape ora belt shape (long shape). The fibrous sheet may have a single layerstructure or a multilayer structure including two or more fibrouslayers.

As means for imparting stretchability and extensibility to the fibroussheet, there are 1) a method of subjecting a fibrous sheet substratesuch as a woven fabric, a nonwoven fabric, or a knit to gathering, and2) a method using crimped fibers crimped into a coil shape as at leastsome fibers constituting a nonwoven fabric. As described above, themethod of weaving, into a fibrous sheet, yarn formed of a stretchablematerial such as an elastomer typified by rubber and the method ofcombining a layer formed of a stretchable material such as an elastomerwith a nonstretchable fibrous sheet substrate or impregnating anonstretchable fibrous sheet substrate with a stretchable material causeproblems such as blood circulation disturbance and pain when the fibroussheet is wrapped around an application site for a long time.

From the viewpoint of self-adhesiveness, hand cut property, ease ofbending of a joint exhibited when the fibrous sheet is wrapped aroundthe joint, conformity (fitting property) with a concavo-convex site suchas a joint exhibited when the fibrous sheet is wrapped around theconcavo-convex site, etc., the fibrous sheet is preferably constitutedof a nonwoven fabric, namely, the fibrous sheet is preferably a nonwovenfabric sheet. More preferably, the fibrous sheet is constituted of anonwoven fabric containing crimped fibers crimped into a coil shape, andstill more preferably, the fibrous sheet is constituted of a nonwovenfabric that contains the crimped fibers and that is an ungatherednonwoven fabric. Particularly preferably, the nonwoven fabric sheet isconstituted only of the crimped fibers.

It is preferable that the fibrous sheet constituted of the nonwovenfabric containing the crimped fibers has a structure in which therespective fibers constituting this nonwoven fabric are notsubstantially fusion-bonded, but mainly the crimped fibers are entangledwith each other at their crimped coil portions and bound or hooked.Further, it is preferable that most (the majority of) crimped fibers(axial direction of crimped fibers) are oriented substantially parallelto a sheet surface. In the present specification, “orientedsubstantially parallel to a surface direction” means a state where aportion in which a large number of crimped fibers (axial direction ofcrimped fibers) are locally oriented along a thickness direction is notrepeatedly present, as in for example entanglement by needle punching.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, the crimped fibers are preferably oriented in a certaindirection in the sheet plane (for example, in the above-described firstdirection, preferably in the length direction), and the adjacent orintersecting crimped fibers are entangled with each other at theircrimped coil portions. Even in the thickness direction (or obliquedirection) of the fibrous sheet, the crimped fibers are preferablyslightly entangled with each other. The entanglement of the crimpedfibers can be caused by the process of shrinking a fibrous web as aprecursor of the fibrous sheet.

The nonwoven fabric in which crimped fibers (axial direction of crimpedfibers) are oriented in a certain direction in the sheet plane andentangled exhibits good stretchability (including extensibility) in thisdirection. In the case where the certain direction is, for example, thelength direction, when a tensile force is applied to the stretchablenonwoven fabric in the length direction, the entangled crimped coilportion tends to extend and return to the original coil shape, so thathigh stretchability can be exhibited in the length direction. Thecushioning property and flexibility in the thickness direction can beexpressed by slight entanglement of the crimped fibers in the thicknessdirection of the nonwoven fabric, whereby the nonwoven fabric can havegood touch feeling and texture. The crimped coil portion easilyentangles with another crimped coil portion by contact with a certaindegree of pressure. The self-adhesiveness can be expressed by theentanglement of the crimped coil portions.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, when a tensile force is applied to the orientationdirection of the crimped fiber (for example, in the above-describedfirst direction, preferably in the length direction), the entangledcrimped coil portion extends due to elastic deformation, and when thetensile force is further applied, the fibrous sheet is finallyunwrapped, so that the cutting property (hand cut property) is alsogood.

As described above, the nonwoven fabric capable of constituting thefibrous sheet preferably contains crimped fibers crimped into a coilshape. The crimped fiber is preferably oriented mainly in the surfacedirection of the nonwoven fabric, and further preferably crimpssubstantially evenly in the thickness direction. The crimped fiber canbe constituted of a conjugated fiber in which a plurality of resinshaving different thermal shrinkage factors (or thermal expansioncoefficients) form a phase structure.

The conjugated fiber constituting the crimped fiber is a fiber (latentlycrimped fiber) having an asymmetric or layered (so-called bimetal)structure crimped by heating due to a difference in thermal shrinkagefactor (or thermal expansion coefficient) of a plurality of resins. Theplurality of resins usually have mutually different softening points ormelting points. The plurality of resins can be selected fromthermoplastic resins such as, for example, polyolefin-based resins(e.g., poly-C₂₋₄ olefin-based resins such as low-density, medium-densityor high-density polyethylene and polypropylene); acrylic resins (e.g.,acrylonitrile-based resins having an acrylonitrile unit, such asacrylonitrile-vinyl chloride copolymers); polyvinyl acetal-based resins(e.g., polyvinyl acetal resins); polyvinyl chloride-based resins (e.g.,polyvinyl chloride, vinyl chloride-vinyl acetate copolymers and vinylchloride-acrylonitrile copolymers); polyvinylidene chloride-based resins(e.g., vinylidene chloride-vinyl chloride copolymers and vinylidenechloride-vinyl acetate copolymers); styrene-based resins (e.g.,heat-resistant polystyrene); polyester-based resins (e.g., poly-C₂₋₄alkylene arylate-based resins such as polyethylene terephthalate resins,polytrimethylene terephthalate resins, polybutylene terephthalate resinsand polyethylene naphthalate resins); polyamide-based resins (e.g.,aliphatic polyamide-based resins such as polyamide 6, polyamide 66,polyamide 11, polyamide 12, polyamide 610 and polyamide 612,semi-aromatic polyamide-based resins, and aromatic polyamide-basedresins such as polyphenylene isophthalamide, polyhexamethyleneterephthalamide and poly-p-phenyleneterephthalamide);polycarbonate-based resins (e.g., bisphenol A-type polycarbonate);polyparaphenylene benzobisoxazole resins; polyphenylene sulfide resins;polyurethane-based resins; and cellulose-based resins (e.g., celluloseesters). These thermoplastic resins may contain other copolymerizableunits.

Among the thermoplastic resins, non thermal adhesive resins undermoisture (or heat-resistant hydrophobic resins or nonaqueous resins)having a softening point or melting point greater than or equal to 100°C., such as, for example, polypropylene-based resins, polyester-basedresins and polyamide-based resins are preferable because fibers are notmelted or softened to be fused even when subjected to a heatingtreatment with high-temperature steam. Particularly, aromaticpolyester-based resins and polyamide-based resins are preferable becausethey are excellent in balance among heat resistance, fiber formability,and so on. A resin exposed to surfaces of conjugated fibers constitutinga nonwoven fabric (latently crimped fiber) is preferably at least a nonthermal adhesive resin under moisture so that the conjugated fibers arenot fused even when treated with high-temperature steam.

The plurality of resins forming the conjugated fiber may have differentthermal shrinkage factors, and may be a combination of resins of thesame kind, or a combination of different kinds of resins.

Preferably, the plurality of resins forming the conjugated fiber are acombination of resins of the same kind from the viewpoint ofadhesiveness. In the case of the combination of resins of the same kind,usually a combination of a component (A) forming a homopolymer(essential component) and a component (B) forming a modification polymer(copolymer) is used. That is, for example, a copolymerizable monomer forreducing the crystallization degree, the melting point, the softeningpoint, or the like is copolymerized with the homopolymer as an essentialcomponent to perform modification, whereby the crystallization degreemay be reduced as compared to the homopolymer, or the polymer may bemade noncrystalline to reduce the melting point or softening point ascompared to the homopolymer. When the crystallization degree, themelting point, or the softening point is changed as described above,this can cause a difference in thermal shrinkage factor. The differencein melting point or softening point is, for example, 5 to 150° C., andpreferably 40 to 130° C., more preferably 60 to 120° C. A ratio of thecopolymerizable monomer to be used for modification is, for example, 1to 50 mol %, preferably 2 to 40 mol %, more preferably 3 to 30 mol %(particularly 5 to 20 mol %) based on the whole amount of monomers.While a mass ratio between the component forming a homopolymer and thecomponent forming a modification polymer can be selected according tothe structure of fibers, the homopolymer component (A)/the modificationpolymer component (B) is for example 90/10 to 10/90, and preferably70/30 to 30/70, more preferably 60/40 to 40/60.

The conjugated fiber is preferably a combination of aromaticpolyester-based resins, more preferably a combination of a polyalkylenearylate-based resin (a) and a modified polyalkylene arylate-based resin(b) because latently crimpable conjugated fibers are easily produced.The polyalkylene arylate-based resin (a) can be a homopolymer of anaromatic dicarboxylic acid (e.g., a symmetric aromatic dicarboxylic acidsuch as terephthalic acid or naphthalene-2,6-dicarboxylic acid) and analkanediol component (e.g., C₂₋₆ alkanediol such as ethylene glycol orbutylene glycol). Specifically, a poly-C₂₋₄ alkylene terephthalate-basedresin such as polyethylene terephthalate (PET) or polybutyleneterephthalate (PBT), or the like is used, and usually, PET for use ingeneral PET fibers having an intrinsic viscosity of 0.6 to 0.7 is used.

On the other hand, in the modified polyalkylene arylate-based resin (b),examples of a copolymerization component for reducing the melting pointor softening point and the crystallization degree of the polyalkylenearylate-based resin (a) as an essential component include dicarboxylicacid components such as an asymmetric aromatic dicarboxylic acid, analicyclic dicarboxylic acid and an aliphatic dicarboxylic acid; analkanediol component having a chain length longer than that ofalkanediol of the polyalkylene arylate-based resin (a); and/or an etherbond-containing diol component. The copolymerization components may beused singly, or in combination of two or more kinds thereof. Among thesecomponents, as the dicarboxylic acid component, asymmetric aromaticdicarboxylic acids (e.g., isophthalic acid, phthalic acid and 5-sodiumsulfoisophthalic acid), aliphatic dicarboxylic acids (C₆₋₁₂ aliphaticdicarboxylic acids such as adipic acid), or the like are generally used.As the diol component, alkanediols (e.g., C₃₋₆ alkanediols such as1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and neopentyl glycol),polyoxyalkylene glycols (e.g., polyoxy-C₂₋₄ alkylene glycols such asdiethylene glycol, triethylene glycol, polyethylene glycol andpolytetramethylene glycol) or the like are generally used. Among them,asymmetric aromatic dicarboxylic acids such as isophthalic acid, andpolyoxy-C₂₋₄ alkylene glycols such as diethylene glycol are preferable.The modified polyalkylene arylate-based resin (b) may be an elastomerhaving a C₂₋₄ alkylene arylate (e.g., ethylene terephthalate or butyleneterephthalate) as a hard segment and a polyoxyalkylene glycol or thelike as a soft segment.

In the modified polyalkylene arylate-based resin (b), a ratio of thedicarboxylic acid component (e.g., isophthalic acid) for reducing themelting point or softening point is, for example, 1 to 50 mol %,preferably 5 to 50 mol %, more preferably 15 to 40 mol % based on thewhole amount of dicarboxylic acid components constituting the modifiedpolyalkylene arylate-based resin (b). A ratio of the diol component(e.g., diethylene glycol) for reducing the melting point or softeningpoint is, for example, less than or equal to 30 mol %, preferably lessthan or equal to 10 mol % (e.g., 0.1 to 10 mol %) based on the wholeamount of diol components constituting the modified polyalkylenearylate-based resin (b). If the ratio of copolymerization components istoo low, sufficient crimps are not expressed, and thus the formstability and stretchability of the nonwoven fabric after expression ofcrimps are lowered. On the other hand, if the ratio of copolymerizablecomponents is too high, although crimp expressing performance isimproved, it is difficult to stably perform spinning.

The modified polyalkylene arylate-based resin (b) may include, asmonomer components, polyvalent carboxylic acid components such astrimellitic acid and pyromellitic acid, polyol components such asglycerol, trimethylolpropane, trimethylolethane and pentaerythritol, andso on as necessary.

A transverse cross-sectional shape of the conjugated fiber(cross-sectional shape perpendicular to the longitudinal direction ofthe fiber) is not limited to a general solid cross-sectional shape suchas a circular cross-sectional shape or an irregular cross-sectionalshape [flat shape, elliptical shape, polygonal shape, 3 to 14-foliatedshape, T-shape, H-shape, V-shape, dog-bone (1-shape) or the like], andit may be a hollow cross-sectional shape or the like. Usually, thetransverse cross-sectional shape of the conjugated fiber is a circularcross-sectional shape.

Examples of the transverse cross-sectional structure of the conjugatedfiber include phase structures formed of a plurality of resins, such as,for example, structures of core-sheath type, sea-island type, blendtype, parallel type (side-by-side type or multilayer lamination type),radial type (radial lamination type), hollow radial type, block type,random composite type and the like. In particular, a structure in whichphase parts neighbor each other (so-called bimetal structure), and astructure in which a phase structure is asymmetric, such as, forexample, a structure of eccentric core-sheath type or parallel type arepreferable because spontaneous crimps are easily expressed by heating.

In the case where the conjugated fiber has a structure of core-sheathtype such as a structure of eccentric core-sheath type, the core partmay be made from a thermal adhesive resin under moisture (e.g., a vinylalcohol-based polymer such as an ethylene-vinyl alcohol copolymer orpolyvinyl alcohol), or a thermoplastic resin having a low melting pointor softening point (e.g., polystyrene or low-density polyethylene) aslong as there is a difference in thermal shrinkage with the non thermaladhesive resin under moisture of the sheath part situated at thesurface, and thus the fiber can be crimped.

The conjugated fibers have an average fineness of, for example, 0.1 to50 dtex, and preferably 0.5 to 10 dtex, more preferably 1 to 5 dtex. Ifthe fineness is too small, it is difficult to produce fibers themselves,and, in addition, it is difficult to secure fiber strength. Further, itis difficult to express fine coil-shaped crimps in a process ofexpressing crimps. On the other hand, if the fineness is too large,fibers are rigid, so that it is difficult to express sufficient crimps.

The conjugated fibers have an average fiber length of, for example, 10to 100 mm, and preferably 20 to 80 mm, more preferably 25 to 75 mm. Ifthe average fiber length is too short, it is difficult to form a fiberweb, and, in addition, entanglement of crimped fibers is insufficientwhen crimps are expressed, so that it may be difficult to secure thestrength and stretchability of the nonwoven fabric. If the average fiberlength is too long, it is difficult to form a fiber web with a uniformbasis weight, and further, a large number of entanglements of fibers areexpressed at the time of forming the web, so that fibers may obstructone another at the time of expressing crimps, resulting in difficulty inexpression of stretchability. When the average fiber length is withinthe above range, some fibers crimped on the nonwoven fabric surface areappropriately exposed on the nonwoven fabric surface, so that theself-adhesiveness of the nonwoven fabric can be improved. The averagefiber length within the above range is advantageous for obtaining goodhand cut property.

The above-described conjugated fiber is a latently crimped fiber, andwhen the conjugated fibers are heat-treated, crimps are expressed (orappear), and thus the conjugated fibers are fibers having substantiallycoil-shaped (helical or spiral spring-shaped) three-dimensional crimps.

The number of crimps (number of mechanical crimps) before heating is,for example, 0 to 30 crimps/25 mm, preferably 1 to 25 crimps/25 mm, morepreferably 5 to 20 crimps/25 mm. The number of crimps after heating is,for example, greater than or equal to 30 crimps/25 mm (for example 30 to200 crimps/25 mm), and preferably 35 to 150 crimps/25 mm.

As described above, the crimped fibers constituting the nonwoven fabrichave substantially coil-shaped crimps after expression of crimps. Anaverage curvature radius of circles formed by the coils of the crimpedfibers is, for example, 10 to 250 μm, and preferably 20 to 200 morepreferably 50 to 160 μm. The average curvature radius is an indexexpressing an average size of circles formed by the coils of crimpedfibers, and in the case where this value is large, the formed coil has aloose shape, i.e., a shape having a small number of crimps. If thenumber of crimps is small, the number of entanglements of crimped fibersalso decreases, and it is difficult to recover the shape againstdeformation of the coil shape, so that it is disadvantageous forexpressing sufficient stretching performance. If the average curvatureradius is too small, crimped fibers are not satisfactorily entangledwith each other, so that it is difficult to secure web strength.Further, when the coil shape is deformed, stress is too large andbreaking strength is excessively increased, so that it is difficult toobtain suitable stretchability.

In the crimped fibers, an average pitch (average crimp pitch) of thecoil is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, morepreferably 0.05 to 0.2 mm. If the average pitch is excessively large,the number of coil crimps that can be expressed per fiber decreases, sothat sufficient stretchability cannot be exhibited. If the average pitchis excessively small, crimped fibers are not satisfactorily entangledwith each other, so that it becomes difficult to secure the strength ofthe nonwoven fabric.

The nonwoven fabric (fibrous web) may contain other fibers(non-conjugated fibers) in addition to the above-described conjugatedfibers. Specific examples of the non-conjugated fiber include, inaddition to fibers constituted of the above-described non thermaladhesive resin under moisture or thermal adhesive resin under moisture,fibers constituted of cellulose-based fibers [e.g., natural fibers(e.g., cotton, wool, silk, and hemp), semi-synthetic fibers (e.g.,acetate fibers such as triacetate fibers), and regenerated fibers (e.g.,rayon, polynosic, cupra, and lyocell (e.g., registered trademark“Tencel”))] and the like. An average fineness and average fiber lengthof the non-conjugated fibers can be the same as those of the conjugatedfibers. The non-conjugated fibers may be used singly, or in combinationof two or more kinds thereof.

A ratio (mass ratio) of the conjugated fiber and the non-conjugatedfiber is preferably adjusted appropriately so that the stress relaxationrate of the fibrous sheet falls within the above-described range. As theratio, the conjugated fiber/the non-conjugated fiber is, for example,50/50 to 100/0, and preferably 60/40 to 100/0, more preferably 70/30 to100/0, still more preferably 80/20 to 100/0, particularly preferably90/10 to 100/0. A balance between the strength and stretchability orflexibility of the nonwoven fabric can be adjusted by blending thenon-conjugated fibers.

The nonwoven fabric (fibrous web) may contain commonly used additives,such as stabilizers (e.g., thermal stabilizers, ultraviolet absorbers,light stabilizers, and antioxidants), antibacterial agents, deodorants,fragrances, colorants (dyes and pigments), fillers, antistatic agents,flame retardants, plasticizers, lubricants, and crystallization speedretardants. The additives may be used singly, or in combination of twoor more kinds thereof. The additive may be supported to the fibersurface or may be contained in the fiber.

The fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers can be suitably produced by a method including a step(web formation step) of forming fibers containing the above-describedconjugated fibers (latently crimped fibers) into a web and a step(heating step) of heating the fibrous web and crimping the conjugatedfibers.

As a method of forming the fibrous web in the web formation step, it ispossible to use a commonly used method such as a direct method includinga spunbond method or a melt-blow method, a carding method usingmelt-blow fibers, staple fibers, or the like, or a dry method such as anair-lay method. Among them, a carding method using melt-blow fibers orstaple fibers, particularly, a carding method using staple fibers iscommonly used. Examples of the web obtained by using staple fibersinclude a random web, a semi-random web, a parallel web, and across-wrap web.

Prior to the heating step, an entangling step of entangling at leastsome fibers in the fibrous web may be carried out. A nonwoven fabric inwhich crimped fibers are suitably entangled can be obtained in the nextheating step by carrying out the entangling step. Although theentangling method may be a method of mechanically performingentanglement, preferred is a method of performing entanglement byspraying or injecting (blowing) water. The entanglement of the fiberswith water flow is advantageous in increasing the density of theentanglement by crimping in the heating step. Although the water to besprayed or injected may be blown from one or both sides of the fibrousweb, it is preferable to blow water from both sides from the viewpointof efficiently performing strong entanglement.

A jetting pressure of water in the entangling step is, for example,greater than or equal to 2 MPa, preferably 3 to 12 MPa, more preferably4 to 10 MPa, so that the fiber entanglement falls within an appropriaterange. A temperature of the sprayed or injected water is, for example, 5to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water, preferred is a method ofinjecting water with use a nozzle or the like having a regular sprayarea or spray pattern, from the viewpoint of convenience and the like.Specifically, water can be injected onto a fibrous web transferred by abelt conveyor such as an endless conveyor, while the fibrous web isplaced on a conveyor belt. The conveyor belt may be water-permeable, andwater may pass through the water-permeable conveyor belt from the backside of the fibrous web to be injected onto the fibrous web. In order tosuppress scattering of fibers due to water injecting, the fibrous webmay be wetted with a small amount of water in advance.

As the nozzle for spraying or injecting water, a plate or die havingpredetermined orifices successively arranged in a width directionthereof is used, and the plate or die may be disposed to arrange theorifices in the width direction of the fibrous web to be conveyed. Thenumber of orifice lines may be at least one, and a plurality of orificelines may be arranged in parallel. A plurality of nozzle dies eachhaving one orifice line may be installed in parallel.

Prior to the entangling step, a step (uneven distribution step) ofunevenly distributing the fibers in the fibrous web in the plane may beprovided. When this step is carried out, a region where fiber densitybecomes sparse is formed in the fibrous web, and therefore, in the casewhere the entangling step is water flow entanglement, a water flow canbe efficiently injected into the fibrous web, so that moderateentanglement can be easily realized not only on a surface of the fibrousweb but also inside thereof.

The uneven distribution step can be performed by spraying or injectinglow-pressure water onto the fibrous web. The low-pressure water may besuccessively sprayed or injected onto the fibrous web, but it ispreferable that the low-pressure water is intermittently or periodicallysprayed onto the fibrous web. When water is intermittently orperiodically sprayed onto the fibrous web, it is possible toperiodically and alternately form a plurality of low-density portionsand a plurality of high-density portions.

It is desirable that a jetting pressure of water in the unevendistribution step is as low as possible, and the jetting pressure ofwater is, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, morepreferably 0.6 to 1.0 MPa. A temperature of the sprayed or injectedwater is, for example, 5 to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water intermittently orperiodically, there is no particular limitation as long as it is amethod capable of periodically and alternately forming a gradient ofdensity on the fibrous web; however, from the viewpoint of convenienceand the like, preferred is a method of injecting water through aplate-like object (e.g., porous plate) having a regular spray area orspray pattern formed with a plurality of holes.

In the heating step, the fibrous web is heated with high temperaturesteam and crimped. In the method of treating the fibrous web with hightemperature steam, the fibrous web is exposed to a high temperature orsuperheated steam (high pressure steam) flow, whereby coil crimps occurin the conjugated fibers (latently crimped fibers). The fibrous web hasair permeability. Accordingly, high temperature steam permeates into thefibrous web even in treatment from one direction, substantially uniformcrimps are expressed in the thickness direction, and the fibers areuniformly entangled with each other.

The fibrous web shrinks simultaneously with high temperature steamtreatment. Accordingly, it is desirable that the fibrous web to besupplied is overfed according to the area shrinkage ratio of an intendednonwoven fabric immediately before the fibrous web is exposed to hightemperature steam. A ratio of the overfeeding is 110 to 300%, preferably120 to 250%, based on the length of the intended nonwoven fabric.

In order to supply the fibrous web with steam, a commonly used steaminjecting apparatus may be used. The steam injecting apparatus ispreferably an apparatus capable of generally uniformly blowing steamover the whole width of the fibrous web with a desired pressure andamount. The steam injecting apparatus may be provided only on onesurface side of the fibrous web, or in order to treat the front and backof the fibrous web with steam at a time, the steam spraying apparatusmay be further provided on the other surface side.

Since the high temperature steam injected from the steam injectingapparatus is a gas flow, the high temperature steam enters inside thefibrous web without significantly moving the fibers in the fibrous web,unlike the water flow entanglement treatment and the needle punchingtreatment. By virtue of the entry action of the steam flow into thefibrous web, the steam flow efficiently covers a surface of each fiberexisting in the fibrous web, and enables uniform thermal crimping. Sinceheat can be satisfactorily conducted inside the fibrous web, as comparedwith the dry heat treatment, the degree of crimping is almost uniform inthe plane direction and the thickness direction.

Similarly to the nozzle for water flow entanglement, as a nozzle forinjecting high temperature steam, a plate or die having predeterminedorifices successively arranged in a width direction thereof is used, andthe plate or die may be disposed to arrange the orifices in the widthdirection of the fibrous web to be conveyed. The number of orifice linesmay be at least one, and a plurality of orifice lines may be arranged inparallel. A plurality of nozzle dies each having one orifice line may beinstalled in parallel.

A pressure of the high temperature steam to be used can be selected fromthe range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). If the pressureof the steam is too high, the fibers forming the fibrous web may movemore than required to cause disturbance of the texture, or the fibersmay be intermingled more than required. When the pressure is too weak,it becomes impossible to give the quantity of heat required forexpression of crimps of the fibers to the fibrous web, or the steamcannot penetrate the fibrous web and expression of crimps of the fibersin the thickness direction tends to be nonuniform. Although depending onmaterials of the fibers and the like, a temperature of the hightemperature steam can be selected from the range of 70 to 180° C. (forexample, 80 to 150° C.). A treatment speed with high temperature steamcan be selected from the range of less than or equal to 200 m/minute(for example, 0.1 to 100 m/minute).

After thus causing expression of crimps of the conjugated fiber in thefibrous web, there may be a case where water remains in the nonwovenfabric, and therefore, a drying step of drying the nonwoven may beprovided as necessary. Examples of the drying method may include amethod using a drying apparatus such as a cylinder dryer or a tenter; anon-contact method such as far infrared ray irradiation, microwaveirradiation, or electron beam irradiation; a method of blowing hot airor passing the nonwoven fabric through hot air, and the like.

Examples of a method of adjusting the stress relaxation rate to theabove-described range in the method of producing a fibrous sheet asdescribed above may include a method of adjusting a content ratio of theconjugated fibers and the non-conjugated fibers; a method of adjustingconditions of the high temperature steam (in particular, temperatureand/or pressure) used in the heating step; a method of adjusting thedrying temperature in the drying step; and the like.

Second Embodiment

(1) Characteristics of Fibrous Sheet

A fibrous sheet according to the present embodiment (hereinafter alsosimply referred to as the “fibrous sheet”) is a fibrous sheet capable ofbeing suitably used not only as a general bandage but also as a medicalarticle such as a compression bandage used for hemostasis, compressiontherapy, and so on. When a thickness of a single fibrous sheet measuredin accordance with A method specified in HS L 1913 (load: 0.5 kPa) isdefined as T₁ [mm], and a thickness of three superimposed sheetsmeasured under the same conditions is defined as T₃ [mm], the fibroussheet satisfies the following formula [A]:

{T ₃/(3×T ₁)}×100≤85[%]  [A].

The fibrous sheet satisfying the above formula [A] is less liable todisturb the bending motion of a site to be bent and stretched, such as ajoint part, even if the fibrous sheet is wrapped around the site. Whenthis site is for example a small joint part of a finger or the like,difficulty in moving the site is remarkable when the fibrous sheet iswrapped around the site. However, according to the fibrous sheetsatisfying the above formula [A], it is possible to effectively preventthe bending motion from being disturbed, even when the fibrous sheet iswrapped around such a small joint part. From the viewpoint of ease ofbending of a site to be bent and stretched when the fibrous sheet iswrapped around the site, the left side of the above formula [A] ispreferably less than or equal to 84%, more preferably less than or equalto 83%. The left side of the above formula [A] is usually greater thanor equal to 50%, more typically greater than or equal to 60%.

As another means for suppressing the disturbance of the bending motion,it is conceivable to reduce a basis weight of the fibrous sheet.However, if the basis weight is reduced, the strength of the fibroussheet decreases, and for example, the abrasion resistance of an outerexposed portion is reduced when the fibrous sheet is wrapped around anapplication site, or the fibrous sheet tends to be broken when extended;thus, it becomes difficult to obtain sufficient durability. On the otherhand, according to the fibrous sheet satisfying the above formula [A],it is possible to suppress the disturbance of the bending motionregardless of the basis weight adjustment. Accordingly, the inventionaccording to the present embodiment can also provide a fibrous sheetcapable of suppressing the disturbance of the bending motion and havinggood durability.

From the viewpoint of ease of bending of a site to be bent and stretchedwhen the fibrous sheet is wrapped around the site, the fibrous sheetpreferably has extensibility. As described above, in the presentspecification, “extensible/having extensibility” means that a stress at50% extension is exhibited in at least one direction (first direction)in the sheet plane. The stress at 50% extension is a stress at extensionat the time of extension at 50% elongation (immediately after extension)and is measured by a tensile test in accordance with the “Test methodsfor nonwovens” specified in JIS L 1913.

When the fibrous sheet is a bandage having, for example, a lengthdirection and a width direction and it is assumed that the bandage iswrapped around a joint part of a finger or the like, the bandage isgenerally wrapped such that its width direction and the length directionof the finger are parallel or approximately parallel to each other. Inthis case, in order to improve ease of bending of the finger joint part,it is preferable that the bandage has good extensibility at least in thewidth direction. From such a viewpoint, when the fibrous sheet has, forexample, a length direction and a width direction like a bandage, thefirst direction is preferably the width direction of the fibrous sheet.This width direction may be a direction orthogonal to a flow direction(MID direction) of the fibrous sheet in a production process, that is, aCD direction.

As described above, the fibrous sheet is excellent in extensibilitypreferably in at least one direction (first direction) in the sheetplane, more preferably in the width direction. More specifically, when astress at extension at the time of extension in the first direction at50% elongation is defined as stress S₁ (N/50 mm) at 50% extension, and astress at extension at the time of extension in a second directionorthogonal to the first direction in a plane at 50% elongation isdefined as stress S₂ (N/50 mm) at 50% extension, the fibrous sheetsatisfies the following formula [B]:

S ₂ /S ₁≥3  [B].

The left side of the above formula [B] is preferably greater than orequal to 5. The left side of the above formula [B] is usually less thanor equal to 20. According to the fibrous sheet having the firstdirection and satisfying the above formula [B], the disturbance of thebending motion can be more effectively suppressed in a use form in whichthe fibrous sheet is wrapped such that the first direction of thefibrous sheet and, for example, the length direction of the finger areparallel or approximately parallel to each other. The left side of theabove formula [B] is preferably less than or equal to 10 from theviewpoint of imparting relatively good extensibility also in the seconddirection.

The stress S₁ at 50% extension in the first direction is preferably 0.1to 20 N/50 mm, more preferably 0.5 to 15 N/50 mm, further preferably 1to 12 N/50 mm.

When the fibrous sheet has a length direction and a width direction, thesecond direction orthogonal to the first direction in the plane ispreferably the length direction. The length direction may be a flowdirection (MD direction) of the fibrous sheet in a production process.The stress S₂ at 50% extension in the second direction and a stress at50% extension in a direction other than the first direction are eachpreferably 0.5 to 60 N/50 mm, more preferably 1 to 45 N/50 mm, stillmore preferably 2 to 40 N/50 mm.

The fibrous sheet preferably exhibits self-adhesiveness. As describedabove, in the present specification, the “self-adhesiveness” refers to aproperty allowing fibers on a fibrous sheet surface to engage with eachother or come into close contact with each other due to superposition(contact) of the fibers and to be hooked or fixed. The fibrous sheethaving self-adhesiveness is advantageous when the fibrous sheet is abandage or the like. For example, in the case where the fibrous sheet isa bandage, after the bandage is wrapped around an application site, thewrapped fibrous sheets are pressed against each other while beingextended by such an operation that an end of the bandage is overlappedon (or torn and then overlapped on) a bandage surface located under theend, so that the fibrous sheets are joined and fixed to each other,thereby expressing self-adhesiveness.

When the fibrous sheet itself has self-adhesiveness, it is unnecessaryto form a layer formed of a self-adhesive agent such as an elastomer ora pressure-sensitive adhesive on a surface of the fibrous sheet or toprepare separately a fastener for fixing the tip after wrapping. Forexample, Japanese Patent Laying-Open No. 2005-095381 (PTD 4) describesthat an acrylic polymer (claim 1) or a latex (paragraphs [0004] to[0006]) is caused to adhere as a self-adhesive agent to at least oneside of a bandage base material. Formation of a layer formed of anelastomer such as latex on the fibrous sheet surface is effective forenhancing self-adhesiveness.

However, it is preferable that the fibrous sheet according to thepresent embodiment is constituted only of a nonelastomer material. Morespecifically, it is preferable that the fibrous sheet is constitutedonly of fibers. When such a layer formed of an elastomer is formed onthe fibrous sheet surface, gaps on the fibrous sheet surface are sealedwith the elastomer, so that when the fibrous sheets are stacked on eachother, it is difficult for fibers to mesh with each other. Therefore,the thickness T₃ of three superimposed fibrous sheets is notsatisfactorily reduced, and as a result, it tends to be relativelydifficult to satisfy the above formula [A]. The layer formed of anelastomer may induce skin irritation and allergy when wrapped around anapplication site.

The self-adhesiveness of the fibrous sheet can be evaluated by a curvedsurface sliding stress. From the viewpoint of the self-adhesiveness, itis preferable that the fibrous sheet has a curved surface sliding stressof, for example, greater than or equal to 3 N/50 mm, preferably greaterthan or equal to 5 N/50 mm, and the curved surface sliding stress ispreferably higher than breaking strength. Since it is relatively easy tounwrap the wrapped fibrous sheet if desired, the curved surface slidingstress is preferably less than or equal to 30 N/50 mm, more preferablyless than or equal to 25 N/50 mm. The curved surface sliding stress ismeasured using a tensile tester in accordance with the method describedin Examples section (FIGS. 1 to 3).

The fibrous sheet preferably has a hand cut property. As describedabove, in the present specification, the “hand cut property” refers to aproperty enabling breakage (cutting) by hand tension. The hand cutproperty of the fibrous sheet can be evaluated by breaking strength.From the viewpoint of the hand cut property, the fibrous sheet has abreaking strength in at least one direction in the sheet plane ofpreferably 5 to 100 N/50 mm, more preferably 8 to 60 N/50 mm, furtherpreferably 10 to 40 N/50 mm. When the breaking strength is within theabove range, it is possible to impart a good hand cut property enablingrelatively easy breakage (cutting) by hand. If the breaking strength istoo large, the hand cut property deteriorates, making it difficult tocut the fibrous sheet with one hand, for example. On the other hand, ifthe breaking strength is too small, the strength of the fibrous sheetbecomes insufficient to cause easy breakage of the fibrous sheet, anddurability and handleability are lowered. The breaking strength ismeasured by a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913.

At least one direction in the sheet plane is a tensile direction whenthe fibrous sheet is cut by hand, and is preferably the above-describedsecond direction. The second direction may be the MD direction, and whenthe fibrous sheet has, for example, a length direction and a widthdirection like a bandage, the first direction is preferably the lengthdirection of the fibrous sheet. That is, when the fibrous sheet is usedas a bandage, it is usual to break the bandage in the length directionafter the bandage is wrapped around an application site while beingextended along the length direction thereof, and therefore the seconddirection is preferably the length direction as the tensile direction.

The breaking strength in a direction other than at least one directionin the sheet plane, for example, the first direction (such as the CDdirection), or a width direction when the fibrous sheet has a lengthdirection and the width direction like a bandage is, for example, 0.1 to300 N/50 mm, preferably 0.5 to 100 N/50 mm, more preferably 1 to 20 N/50mm.

From the viewpoint of the hand cut property, it is preferable that thefibrous sheet is constituted only of a non-elastomer material. Morespecifically, it is preferable that the fibrous sheet is constitutedonly of fibers. If a layer formed of an elastomer, etc. is formed on thefibrous sheet surface, the hand cut property may be lowered.

The fibrous sheet has an elongation at break in at least one directionin the sheet plane of, for example, greater than or equal to 50%,preferably greater than or equal to 60%, more preferably greater than orequal to 80%. When the elongation at break is within the above range, itis advantageous for enhancing the stretchability of the fibrous sheet.The elongation at break in at least one direction in the sheet plane isusually less than or equal to 300% and preferably less than or equal to250%. The elongation at break is also measured by a tensile test inaccordance with the “Test methods for nonwovens” specified in JIS L1913.

From the viewpoint of ease of bending of a site to be bent andstretched, such as a joint part, when the fibrous sheet is wrappedaround the site, at least one direction in the sheet plane is preferablythe above-described first direction. The first direction may be the CDdirection, and when the fibrous sheet has, for example, a lengthdirection and a width direction like a bandage, the first direction ispreferably the width direction of the fibrous sheet.

The elongation at break in a direction other than at least one directionin the sheet plane, for example, the second direction (such as the MDdirection), or a length direction when the fibrous sheet has the lengthdirection and a width direction like a bandage is, for example, 10 to500%, preferably 100 to 350%.

The fibrous sheet has a recovery rate after 50% extension in at leastone direction in the sheet plane (recovery rate after 50% extension) ispreferably greater than or equal to 70% (less than or equal to 100%),more preferably greater than or equal to 80%, further preferably greaterthan or equal to 90%. When the recovery rate after 50% extension iswithin the range, the followability to extension is enhanced, and forexample when the fibrous sheet is wrapped around a site to be bent andstretched, such as a joint part, the fibrous sheet satisfactorilyfollows the bending motion and shape of the site, and at the same time,it is advantageous for improvement of the self-adhesiveness due tofriction between the overlapped fibrous sheets. If the extensionrecovery rate is excessively small, the fibrous sheet cannot follow thebending motion of the site, and deformation of the fibrous sheet causedby this motion does not return to its original shape, thus weakeningfixation of the wrapped fibrous sheet.

At least one direction in the sheet plane is preferably theabove-described first direction where the followability to the bendingmotion of a site to be bent and stretched, such as a joint part, isparticularly required when the fibrous sheet is wrapped around the site.The first direction may be the CD direction, and when the fibrous sheethas, for example, a length direction and a width direction like abandage, the first direction is preferably the width direction of thefibrous sheet.

The recovery rate after 50% extension is defined by the followingformula:

Recovery rate after 50% extension (%)=100−X

when, in a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913, a residual strain (%) after the testis defined as X when load is removed immediately after the elongationrate reaches 50%.

The recovery rate after 50% extension in a direction other than at leastone direction in the sheet plane, for example, the second direction(such as the MD direction), or a length direction when the fibrous sheethas the length direction and a width direction like a bandage is, forexample, greater than or equal to 70% (less than or equal to 100%),preferably greater than or equal to 80%.

The fibrous sheet has a compression elastic modulus Pe of preferablyless than or equal to 85%, more preferably less than or equal to 80%. Itis advantageous for satisfying the above formula [A] that thecompression elastic modulus Pe is within this range, and consequently itis advantageous in achieving a fibrous sheet less likely to disturb thebending motion of a joint part or the like. A lower limit of thecompression elastic modulus Pe is not particularly limited, and is, forexample, 50%. The compression elastic modulus Pe is calculated inaccordance with the “Test methods for nonwovens” specified in JIS L 1913by the following formula [C]:

Pe={(T ₁ ′−T)/(T ₁ −T)}×100  [C].

T₁ is the thickness [mm] when an initial load (0.5 kPa) is applied, andhas the same meaning as T₁ in the above formula [A]. T is the thickness[mm] when a load of 30 kPa is applied. T₁′ is the thickness [mm] whenthe initial load is restored.

The fibrous sheet has a basis weight of preferably 30 to 300 g/m², morepreferably 50 to 200 g/m². From the viewpoint of more effectivelysuppressing the disturbance of the bending motion, the basis weight ismore preferably less than or equal to 180 g/m². According to the fibroussheet of the present embodiment, even when the basis weight is large(for example, greater than or equal to 50 g/m², greater than or equal to70 g/m², greater than or equal to 90 g/m², greater than or equal to 110g/m², further greater than or equal to 130 g/m²), it is possible toeffectively suppress the disturbance of the bending motion of a jointpart or the like.

The thickness T₁ of the fibrous sheet (the thickness T₁ has the samemeaning as T₁ in the above formula [A]) is, for example, 0.2 to 5 mm,preferably 0.3 to 3 mm, more preferably 0.4 to 2 mm. When the basisweight and the thickness are within these ranges, a balance among theease of bending exhibited when wrapping the fibrous sheet, theextensibility, and the flexibility, touch feeling and cushioningproperty of the fibrous sheet is good. A density (bulk density) of thefibrous sheet can be a value corresponding to the above-described basisweight and thickness, and the density (bulk density) is, for example,0.03 to 0.5 g/cm³, preferably 0.04 to 0.4 g/cm³, more preferably 0.05 to0.2 g/cm³. From the viewpoint of more effectively suppressing thedisturbance of the bending motion, the density is more preferably lessthan or equal to 0.15 g/cm³.

In the fibrous sheet, a difference ΔT between the thickness T₁ when theinitial load (0.5 kPa) is applied and the thickness T when a load of 30kPa is applied is preferably greater than or equal to 0.05 mm, morepreferably greater than or equal to 0.1 mm. It is advantageous forsatisfying the above formula [A] that the thickness difference ΔT is inthis range, and consequently it is advantageous in achieving a fibroussheet less likely to disturb the bending motion of a joint part or thelike. The thickness difference ΔT corresponds to (T₁−T) in the aboveformula [C]. An upper limit of the thickness difference ΔT is notparticularly limited, and is, for example, 0.8 mm.

The fibrous sheet has an air permeability measured by the Frazier methodof preferably greater than or equal to 0.1 cm³/(cm²·second), morepreferably 1 to 500 cm³/(cm²·second), further preferably 5 to 300cm³/(cm²·second), particularly preferably 10 to 200 cm³/(cm²·second).When the air permeability is within this range, the fibrous sheet ismore suitably used for the human body, such as a bandage, because thefibrous sheet is good in air permeability and is hardly stuffy.

(2) Structure and Production Method of Fibrous Sheet

The fibrous sheet of the present embodiment is not particularly limitedas long as it is constituted of fibers, and the fibrous sheet may be,for example, a woven fabric, a nonwoven fabric, a knit (knitted fabric),or the like. Although the shape of the fibrous sheet can be selectedaccording to use application, it is preferably a rectangular sheet shapehaving a length direction and a width direction such as a tape shape ora belt shape (long shape). The fibrous sheet may have a single layerstructure or a multilayer structure including two or more fibrouslayers.

Examples of means for imparting stretchability and extensibility to thefibrous sheet may include 1) a method of subjecting a fibrous sheetsubstrate such as a woven fabric, a nonwoven fabric, or a knit togathering; 2) a method of weaving, into a fibrous sheet, yarn formed ofa stretchable material such as an elastomer typified by rubber; 3) amethod of combining a layer formed of a stretchable material such as anelastomer with a nonstretchable fibrous sheet substrate or impregnatinga nonstretchable fibrous sheet substrate with a stretchable material; 4)a method using crimped fibers crimped into a coil shape as at least somefibers constituting a nonwoven fabric; and the like.

Among the above methods, the fibrous sheet according to the presentembodiment is preferably obtained by using the method described in 4).Although the gathering described in 1) is effective in thatstretchability can be effectively imparted to the fibrous sheet, it isrelatively difficult to obtain a fibrous sheet satisfying the aboveformula [A] depending on the wavy shape of the gather. According to themethod 2), stretchability can be easily imparted to the fibrous sheet;however, since a rubber yarn or the like is woven, there is a fear thatease of bending exhibited when wrapping the fibrous sheet may bedeteriorated. As described above, the method 3) tends to make itrelatively difficult to satisfy the above formula [A] by sealing thefibrous sheet surface with the elastomer.

From the viewpoint of ease of bending of a joint part exhibited when thefibrous sheet is wrapped around the joint part, self-adhesiveness, handcut property, conformity (fitting property) with a concavo-convex sitesuch as a joint exhibited when the fibrous sheet is wrapped around theconcavo-convex site, etc., the fibrous sheet is preferably constitutedof a nonwoven fabric, namely, the fibrous sheet is preferably a nonwovenfabric sheet. More preferably, the fibrous sheet is constituted of anonwoven fabric containing crimped fibers crimped into a coil shape, andstill more preferably, the fibrous sheet is constituted of a nonwovenfabric that contains the crimped fibers and that is not subjected to atleast one of treatments (desirably all treatments) described in 1) to3). Particularly preferably, the nonwoven fabric sheet is constitutedonly of the crimped fibers.

It is preferable that the fibrous sheet constituted of the nonwovenfabric containing the crimped fibers has a structure in which therespective fibers constituting this nonwoven fabric are notsubstantially fusion-bonded, but mainly the crimped fibers are entangledwith each other at their crimped coil portions and bound or hooked.Further, it is preferable that most (the majority of) crimped fibers(axial direction of crimped fibers) are oriented substantially parallelto a sheet surface. As described above, in the present specification,“oriented substantially parallel to a surface direction” means a statewhere a portion in which a large number of crimped fibers (axialdirection of crimped fibers) are locally oriented along a thicknessdirection is not repeatedly present, as in for example entanglement byneedle punching.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, the crimped fibers are preferably oriented in a certaindirection in the sheet plane (for example, in the above-described seconddirection, preferably in the length direction), and the adjacent orintersecting crimped fibers are entangled with each other at theircrimped coil portions. Even in the thickness direction (or obliquedirection) of the fibrous sheet, the crimped fibers are preferablyslightly entangled with each other. The entanglement of the crimpedfibers can be caused by the process of shrinking a fibrous web as aprecursor of the fibrous sheet.

The nonwoven fabric in which crimped fibers (axial direction of crimpedfibers) are oriented in a certain direction in the sheet plane andentangled exhibits good stretchability (including extensibility) in thisdirection. In the case where the certain direction is, for example, thelength direction, when a tensile force is applied to the stretchablenonwoven fabric in the length direction, the entangled crimped coilportion tends to extend and return to the original coil shape, so thathigh stretchability can be exhibited in the length direction. Thisstretchable nonwoven fabric can exhibit excellent extensibility in adirection (for example, the width direction) orthogonal to the certaindirection in the sheet plane. The cushioning property and flexibility inthe thickness direction can be expressed by slight entanglement of thecrimped fibers in the thickness direction of the nonwoven fabric,whereby the nonwoven fabric can have good touch feeling and texture. Thecrimped coil portion easily entangles with another crimped coil portionby contact with a certain degree of pressure. The self-adhesiveness canbe expressed by the entanglement of the crimped coil portions.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, when a tensile force is applied to the orientationdirection of the crimped fiber (for example, in the above-describedsecond direction, preferably in the length direction), the entangledcrimped coil portion extends due to elastic deformation, and when thetensile force is further applied, the fibrous sheet is finallyunwrapped, so that the cutting property (hand cut property) is alsogood.

As described above, the nonwoven fabric capable of constituting thefibrous sheet preferably contains crimped fibers crimped into a coilshape. The crimped fiber is preferably oriented mainly in the surfacedirection of the nonwoven fabric, and further preferably crimpssubstantially evenly in the thickness direction. The crimped fiber canbe constituted of a conjugated fiber in which a plurality of resinshaving different thermal shrinkage factors (or thermal expansioncoefficients) form a phase structure.

The conjugated fiber constituting the crimped fiber is a fiber (latentlycrimped fiber) having an asymmetric or layered (so-called bimetal)structure crimped by heating due to a difference in thermal shrinkagefactor (or thermal expansion coefficient) of a plurality of resins. Theplurality of resins usually have mutually different softening points ormelting points. The plurality of resins can be selected fromthermoplastic resins such as, for example, polyolefin-based resins(e.g., poly-C₂₋₄ olefin-based resins such as low-density, medium-densityor high-density polyethylene and polypropylene); acrylic resins (e.g.,acrylonitrile-based resins having an acrylonitrile unit, such asacrylonitrile-vinyl chloride copolymers); polyvinyl acetal-based resins(e.g., polyvinyl acetal resins); polyvinyl chloride-based resins (e.g.,polyvinyl chloride, vinyl chloride-vinyl acetate copolymers and vinylchloride-acrylonitrile copolymers); polyvinylidene chloride-based resins(e.g., vinylidene chloride-vinyl chloride copolymers and vinylidenechloride-vinyl acetate copolymers); styrene-based resins (e.g.,heat-resistant polystyrene); polyester-based resins (e.g., poly-C₂₋₄alkylene arylate-based resins such as polyethylene terephthalate resins,polytrimethylene terephthalate resins, polybutylene terephthalate resinsand polyethylene naphthalate resins); polyamide-based resins (e.g.,aliphatic polyamide-based resins such as polyamide 6, polyamide 66,polyamide 11, polyamide 12, polyamide 610 and polyamide 612,semi-aromatic polyamide-based resins, and aromatic polyamide-basedresins such as polyphenylene isophthalamide, polyhexamethyleneterephthalamide and poly-p-phenyleneterephthalamide);polycarbonate-based resins (e.g., bisphenol A-type polycarbonate);polyparaphenylene benzobisoxazole resins; polyphenylene sulfide resins;polyurethane-based resins; and cellulose-based resins (e.g., celluloseesters). These thermoplastic resins may contain other copolymerizableunits.

Among the thermoplastic resins, non thermal adhesive resins undermoisture (or heat-resistant hydrophobic resins or nonaqueous resins)having a softening point or melting point greater than or equal to 100°C., such as, for example, polypropylene-based resins, polyester-basedresins and polyamide-based resins are preferable because fibers are notmelted or softened to be fused even when subjected to a heatingtreatment with high-temperature steam. Particularly, aromaticpolyester-based resins and polyamide-based resins are preferable becausethey are excellent in balance among heat resistance, fiber formability,and so on. A resin exposed to surfaces of conjugated fibers constitutinga nonwoven fabric (latently crimped fiber) is preferably at least a nonthermal adhesive resin under moisture so that the conjugated fibers arenot fused even when treated with high-temperature steam.

The plurality of resins forming the conjugated fiber may have differentthermal shrinkage factors, and may be a combination of resins of thesame kind, or a combination of different kinds of resins.

Preferably, the plurality of resins forming the conjugated fiber are acombination of resins of the same kind from the viewpoint ofadhesiveness. In the case of the combination of resins of the same kind,usually a combination of a component (A) forming a homopolymer(essential component) and a component (B) forming a modification polymer(copolymer) is used. That is, for example, a copolymerizable monomer forreducing the crystallization degree, the melting point, the softeningpoint, or the like is copolymerized with the homopolymer as an essentialcomponent to perform modification, whereby the crystallization degreemay be reduced as compared to the homopolymer, or the polymer may bemade noncrystalline to reduce the melting point or softening point ascompared to the homopolymer. When the crystallization degree, themelting point, or the softening point is changed as described above,this can cause a difference in thermal shrinkage factor. The differencein melting point or softening point is, for example, 5 to 150° C., andpreferably 40 to 130° C., more preferably 60 to 120° C. A ratio of thecopolymerizable monomer to be used for modification is, for example, 1to 50 mol %, preferably 2 to 40 mol %, more preferably 3 to 30 mol %(particularly 5 to 20 mol %) based on the whole amount of monomers.While a mass ratio between the component forming a homopolymer and thecomponent forming a modification polymer can be selected according tothe structure of fibers, the homopolymer component (A)/the modificationpolymer component (B) is for example 90/10 to 10/90, and preferably70/30 to 30/70, more preferably 60/40 to 40/60.

The conjugated fiber is preferably a combination of aromaticpolyester-based resins, more preferably a combination of a polyalkylenearylate-based resin (a) and a modified polyalkylene arylate-based resin(b) because latently crimpable conjugated fibers are easily produced.The polyalkylene arylate-based resin (a) can be a homopolymer of anaromatic dicarboxylic acid (e.g., a symmetric aromatic dicarboxylic acidsuch as terephthalic acid or naphthalene-2,6-dicarboxylic acid) and analkanediol component (e.g., C₂₋₆ alkanediol such as ethylene glycol orbutylene glycol). Specifically, a poly-C₂₋₄ alkylene terephthalate-basedresin such as polyethylene terephthalate (PET) or polybutyleneterephthalate (PBT), or the like is used, and usually, PET for use ingeneral PET fibers having an intrinsic viscosity of 0.6 to 0.7 is used.

On the other hand, in the modified polyalkylene arylate-based resin (b),examples of a copolymerization component for reducing the melting pointor softening point and the crystallization degree of the polyalkylenearylate-based resin (a) as an essential component include dicarboxylicacid components such as an asymmetric aromatic dicarboxylic acid, analicyclic dicarboxylic acid and an aliphatic dicarboxylic acid; analkanediol component having a chain length longer than that ofalkanediol of the polyalkylene arylate-based resin (a); and/or an etherbond-containing diol component. The copolymerization components may beused singly, or in combination of two or more kinds thereof. Among thesecomponents, as the dicarboxylic acid component, asymmetric aromaticdicarboxylic acids (e.g., isophthalic acid, phthalic acid and 5-sodiumsulfoisophthalic acid), aliphatic dicarboxylic acids (C₆₋₁₂ aliphaticdicarboxylic acids such as adipic acid), or the like are generally used.As the diol component, alkanediols (e.g., C₃₋₆ alkanediols such as1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and neopentyl glycol),polyoxyalkylene glycols (e.g., polyoxy-C₂₋₄ alkylene glycols such asdiethylene glycol, triethylene glycol, polyethylene glycol andpolytetramethylene glycol) or the like are generally used. Among them,asymmetric aromatic dicarboxylic acids such as isophthalic acid, andpolyoxy-C₂₋₄ alkylene glycols such as diethylene glycol are preferable.The modified polyalkylene arylate-based resin (b) may be an elastomerhaving a C₂₋₄ alkylene arylate (e.g., ethylene terephthalate or butyleneterephthalate) as a hard segment and a polyoxyalkylene glycol or thelike as a soft segment.

In the modified polyalkylene arylate-based resin (b), a ratio of thedicarboxylic acid component (e.g., isophthalic acid) for reducing themelting point or softening point is, for example, 1 to 50 mol %,preferably 5 to 50 mol %, more preferably 15 to 40 mol % based on thewhole amount of dicarboxylic acid components constituting the modifiedpolyalkylene arylate-based resin (b). A ratio of the diol component(e.g., diethylene glycol) for reducing the melting point or softeningpoint is, for example, less than or equal to 30 mol %, preferably lessthan or equal to 10 mol % (e.g., 0.1 to 10 mol %) based on the wholeamount of diol components constituting the modified polyalkylenearylate-based resin (b). If the ratio of copolymerization components istoo low, sufficient crimps are not expressed, and thus the formstability and stretchability of the nonwoven fabric after expression ofcrimps are lowered. On the other hand, if the ratio of copolymerizablecomponents is too high, although crimp expressing performance isimproved, it is difficult to stably perform spinning.

The modified polyalkylene arylate-based resin (b) may include, asmonomer components, polyvalent carboxylic acid components such astrimellitic acid and pyromellitic acid, polyol components such asglycerol, trimethylolpropane, trimethylolethane and pentaerythritol, andso on as necessary.

A transverse cross-sectional shape of the conjugated fiber(cross-sectional shape perpendicular to the longitudinal direction ofthe fiber) is not limited to a general solid cross-sectional shape suchas a circular cross-sectional shape or an irregular cross-sectionalshape [flat shape, elliptical shape, polygonal shape, 3 to 14-foliatedshape, T-shape, H-shape, V-shape, dog-bone (I-shape) or the like], andit may be a hollow cross-sectional shape or the like. Usually, thetransverse cross-sectional shape of the conjugated fiber is a circularcross-sectional shape.

Examples of the transverse cross-sectional structure of the conjugatedfiber include phase structures formed of a plurality of resins, such as,for example, structures of core-sheath type, sea-island type, blendtype, parallel type (side-by-side type or multilayer lamination type),radial type (radial lamination type), hollow radial type, block type,random composite type and the like. In particular, a structure in whichphase parts neighbor each other (so-called bimetal structure), and astructure in which a phase structure is asymmetric, such as, forexample, a structure of eccentric core-sheath type or parallel type arepreferable because spontaneous crimps are easily expressed by heating.

In the case where the conjugated fiber has a structure of core-sheathtype such as a structure of eccentric core-sheath type, the core partmay be made from a thermal adhesive resin under moisture (e.g., a vinylalcohol-based polymer such as an ethylene-vinyl alcohol copolymer orpolyvinyl alcohol), or a thermoplastic resin having a low melting pointor softening point (e.g., polystyrene or low-density polyethylene) aslong as there is a difference in thermal shrinkage with the non thermaladhesive resin under moisture of the sheath part situated at thesurface, and thus the fiber can be crimped.

The conjugated fibers have an average fineness of, for example, 0.1 to50 dtex, and preferably 0.5 to 10 dtex, more preferably 1 to 5 dtex. Ifthe fineness is too small, it is difficult to produce fibers themselves,and, in addition, it is difficult to secure fiber strength. Further, itis difficult to express fine coil-shaped crimps in a process ofexpressing crimps. On the other hand, if the fineness is too large,fibers are rigid, so that it is difficult to express sufficient crimps.

The conjugated fibers have an average fiber length of, for example, 10to 100 mm, and preferably 20 to 80 mm, more preferably 25 to 75 mm. Ifthe average fiber length is too short, it is difficult to form a fiberweb, and, in addition, entanglement of crimped fibers is insufficientwhen crimps are expressed, so that it may be difficult to secure thestrength and stretchability of the nonwoven fabric. If the average fiberlength is too long, it is difficult to form a fiber web with a uniformbasis weight, and further, a large number of entanglements of fibers areexpressed at the time of forming the web, so that fibers may obstructone another at the time of expressing crimps, resulting in difficulty inexpression of stretchability. When the average fiber length is withinthe above range, some fibers crimped on the nonwoven fabric surface areappropriately exposed on the nonwoven fabric surface, so that theself-adhesiveness of the nonwoven fabric can be improved. The averagefiber length within the above range is advantageous for obtaining goodhand cut property.

The above-described conjugated fiber is a latently crimped fiber, andwhen the conjugated fibers are heat-treated, crimps are expressed (orappear), and thus the conjugated fibers are fibers having substantiallycoil-shaped (helical or spiral spring-shaped) three-dimensional crimps.

The number of crimps (number of mechanical crimps) before heating is,for example, 0 to 30 crimps/25 mm, preferably 1 to 25 crimps/25 mm, morepreferably 5 to 20 crimps/25 mm. The number of crimps after heating is,for example, greater than or equal to 30 crimps/25 mm (for example 30 to200 crimps/25 mm), and preferably 35 to 150 crimps/25 mm.

As described above, the crimped fibers constituting the nonwoven fabrichave substantially coil-shaped crimps after expression of crimps. Anaverage curvature radius of circles formed by the coils of the crimpedfibers is, for example, 10 to 250 μm, and preferably 20 to 200 μm, morepreferably 50 to 160 μm. The average curvature radius is an indexexpressing an average size of circles formed by the coils of crimpedfibers, and in the case where this value is large, the formed coil has aloose shape, i.e., a shape having a small number of crimps. If thenumber of crimps is small, the number of entanglements of crimped fibersalso decreases, and it is difficult to recover the shape againstdeformation of the coil shape, so that it is disadvantageous forexpressing sufficient stretching performance. If the average curvatureradius is too small, crimped fibers are not satisfactorily entangledwith each other, so that it is difficult to secure web strength.Further, when the coil shape is deformed, stress is too large andbreaking strength is excessively increased, so that it is difficult toobtain suitable stretchability.

In the crimped fibers, an average pitch (average crimp pitch) of thecoil is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, morepreferably 0.05 to 0.2 mm. If the average pitch is excessively large,the number of coil crimps that can be expressed per fiber decreases, sothat sufficient stretchability cannot be exhibited. If the average pitchis excessively small, crimped fibers are not satisfactorily entangledwith each other, so that it becomes difficult to secure the strength ofthe nonwoven fabric.

The nonwoven fabric (fibrous web) may contain other fibers(non-conjugated fibers) in addition to the above-described conjugatedfibers. Specific examples of the non-conjugated fiber include, inaddition to fibers constituted of the above-described non thermaladhesive resin under moisture or thermal adhesive resin under moisture,fibers constituted of cellulose-based fibers [e.g., natural fibers(e.g., cotton, wool, silk, and hemp), semi-synthetic fibers (e.g.,acetate fibers such as triacetate fibers), and regenerated fibers (e.g.,rayon, polynosic, cupra, and lyocell (e.g., registered trademark“Tencel”))] and the like. An average fineness and average fiber lengthof the non-conjugated fibers can be the same as those of the conjugatedfibers. The non-conjugated fibers may be used singly, or in combinationof two or more kinds thereof.

A ratio (mass ratio) of the conjugated fiber and the non-conjugatedfiber is preferably adjusted appropriately so that the fibrous sheetsatisfies the above formula [A]. As the ratio, the conjugated fiber/thenon-conjugated fiber is, for example, 50/50 to 100/0, and preferably60/40 to 100/0, more preferably 70/30 to 100/0, still more preferably80/20 to 100/0, particularly preferably 90/10 to 100/0. A balancebetween the strength and stretchability or flexibility of the nonwovenfabric can be adjusted by blending the non-conjugated fibers.

The nonwoven fabric (fibrous web) may contain commonly used additives,such as stabilizers (e.g., thermal stabilizers, ultraviolet absorbers,light stabilizers, and antioxidants), antibacterial agents, deodorants,fragrances, colorants (dyes and pigments), fillers, antistatic agents,flame retardants, plasticizers, lubricants, and crystallization speedretardants. The additives may be used singly, or in combination of twoor more kinds thereof. The additive may be supported to the fibersurface or may be contained in the fiber.

The fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers can be suitably produced by a method including a step(web formation step) of forming fibers containing the above-describedconjugated fibers (latently crimped fibers) into a web and a step(heating step) of heating the fibrous web and crimping the conjugatedfibers.

As a method of forming the fibrous web in the web formation step, it ispossible to use a commonly used method such as a direct method includinga spunbond method or a melt-blow method, a carding method usingmelt-blow fibers, staple fibers, or the like, or a dry method such as anair-lay method. Among them, a carding method using melt-blow fibers orstaple fibers, particularly, a carding method using staple fibers iscommonly used. Examples of the web obtained by using staple fibersinclude a random web, a semi-random web, a parallel web, and across-wrap web.

Prior to the heating step, an entangling step of entangling at leastsome fibers in the fibrous web may be carried out. A nonwoven fabric inwhich crimped fibers are suitably entangled can be obtained in the nextheating step by carrying out the entangling step. Although theentangling method may be a method of mechanically performingentanglement, preferred is a method of performing entanglement byspraying or injecting (blowing) water. The entanglement of the fiberswith water flow is advantageous in increasing the density of theentanglement by crimping in the heating step. Although the water to besprayed or injected may be blown from one or both sides of the fibrousweb, it is preferable to blow water from both sides from the viewpointof efficiently performing strong entanglement.

A jetting pressure of water in the entangling step is, for example,greater than or equal to 2 MPa, preferably 3 to 12 MPa, more preferably4 to 10 MPa, so that the fiber entanglement falls within an appropriaterange. A temperature of the sprayed or injected water is, for example, 5to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water, preferred is a method ofinjecting water with use a nozzle or the like having a regular sprayarea or spray pattern, from the viewpoint of convenience and the like.Specifically, water can be injected onto a fibrous web transferred by abelt conveyor such as an endless conveyor, while the fibrous web isplaced on a conveyor belt. The conveyor belt may be water-permeable, andwater may pass through the water-permeable conveyor belt from the backside of the fibrous web to be injected onto the fibrous web. In order tosuppress scattering of fibers due to water injecting, the fibrous webmay be wetted with a small amount of water in advance.

As the nozzle for spraying or injecting water, a plate or die havingpredetermined orifices successively arranged in a width directionthereof is used, and the plate or die may be disposed to arrange theorifices in the width direction of the fibrous web to be conveyed. Thenumber of orifice lines may be at least one, and a plurality of orificelines may be arranged in parallel. A plurality of nozzle dies eachhaving one orifice line may be installed in parallel.

Prior to the entangling step, a step (uneven distribution step) ofunevenly distributing the fibers in the fibrous web in the plane may beprovided. When this step is carried out, a region where fiber densitybecomes sparse is formed in the fibrous web, and therefore, in the casewhere the entangling step is water flow entanglement, a water flow canbe efficiently injected into the fibrous web, so that moderateentanglement can be easily realized not only on a surface of the fibrousweb but also inside thereof.

The uneven distribution step can be performed by spraying or injectinglow-pressure water onto the fibrous web. The low-pressure water may besuccessively sprayed or injected onto the fibrous web, but it ispreferable that the low-pressure water is intermittently or periodicallysprayed onto the fibrous web.

When water is intermittently or periodically sprayed onto the fibrousweb, it is possible to periodically and alternately form a plurality oflow-density portions and a plurality of high-density portions.

It is desirable that a jetting pressure of water in the unevendistribution step is as low as possible, and the jetting pressure ofwater is, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, morepreferably 0.6 to 1.0 MPa. A temperature of the sprayed or injectedwater is, for example, 5 to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water intermittently orperiodically, there is no particular limitation as long as it is amethod capable of periodically and alternately forming a gradient ofdensity on the fibrous web; however, from the viewpoint of convenienceand the like, preferred is a method of injecting water through aplate-like object (e.g., porous plate) having a regular spray area orspray pattern formed with a plurality of holes.

In the heating step, the fibrous web is heated with high temperaturesteam and crimped. In the method of treating the fibrous web with hightemperature steam, the fibrous web is exposed to a high temperature orsuperheated steam (high pressure steam) flow, whereby coil crimps occurin the conjugated fibers (latently crimped fibers). The fibrous web hasair permeability. Accordingly, high temperature steam permeates into thefibrous web even in treatment from one direction, substantially uniformcrimps are expressed in the thickness direction, and the fibers areuniformly entangled with each other.

The fibrous web shrinks simultaneously with high temperature steamtreatment. Accordingly, it is desirable that the fibrous web to besupplied is overfed according to the area shrinkage ratio of an intendednonwoven fabric immediately before the fibrous web is exposed to hightemperature steam. A ratio of the overfeeding is 110 to 300%, preferably120 to 250%, based on the length of the intended nonwoven fabric.

In order to supply the fibrous web with steam, a commonly used steaminjecting apparatus may be used. The steam injecting apparatus ispreferably an apparatus capable of generally uniformly blowing steamover the whole width of the fibrous web with a desired pressure andamount. The steam injecting apparatus may be provided only on onesurface side of the fibrous web, or in order to treat the front and backof the fibrous web with steam at a time, the steam spraying apparatusmay be further provided on the other surface side.

Since the high temperature steam injected from the steam injectingapparatus is a gas flow, the high temperature steam enters inside thefibrous web without significantly moving the fibers in the fibrous web,unlike the water flow entanglement treatment and the needle punchingtreatment. By virtue of the entry action of the steam flow into thefibrous web, the steam flow efficiently covers a surface of each fiberexisting in the fibrous web, and enables uniform thermal crimping. Sinceheat can be satisfactorily conducted inside the fibrous web, as comparedwith the dry heat treatment, the degree of crimping is almost uniform inthe plane direction and the thickness direction.

Similarly to the nozzle for water flow entanglement, as a nozzle forinjecting high temperature steam, a plate or die having predeterminedorifices successively arranged in a width direction thereof is used, andthe plate or die may be disposed to arrange the orifices in the widthdirection of the fibrous web to be conveyed. The number of orifice linesmay be at least one, and a plurality of orifice lines may be arranged inparallel. A plurality of nozzle dies each having one orifice line may beinstalled in parallel.

A pressure of the high temperature steam to be used can be selected fromthe range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). If the pressureof the steam is too high, the fibers forming the fibrous web may movemore than required to cause disturbance of the texture, or the fibersmay be intermingled more than required. When the pressure is too weak,it becomes impossible to give the quantity of heat required forexpression of crimps of the fibers to the fibrous web, or the steamcannot penetrate the fibrous web and expression of crimps of the fibersin the thickness direction tends to be nonuniform. Although depending onmaterials of the fibers and the like, a temperature of the hightemperature steam can be selected from the range of 70 to 180° C. (forexample, 80 to 150° C.). A treatment speed with high temperature steamcan be selected from the range of less than or equal to 200 m/minute(for example, 0.1 to 100 m/minute).

After thus causing expression of crimps of the conjugated fiber in thefibrous web, there may be a case where water remains in the nonwovenfabric, and therefore, a drying step of drying the nonwoven may beprovided as necessary. Examples of the drying method may include amethod using a drying apparatus such as a cylinder dryer or a tenter; anon-contact method such as far infrared ray irradiation, microwaveirradiation, or electron beam irradiation; a method of blowing hot airor passing the nonwoven fabric through hot air, and the like.

Examples of a method for satisfying the above formula [A] in the methodof producing a fibrous sheet as described above may include a method ofadjusting a content ratio of the conjugated fibers and thenon-conjugated fibers; a method of adjusting conditions of the hightemperature steam (in particular, temperature and/or pressure) used inthe heating step; a method of adjusting the drying temperature in thedrying step; and the like.

Third Embodiment

(1) Characteristics of Fibrous Sheet

A fibrous sheet according to the present embodiment (hereinafter alsosimply referred to as the “fibrous sheet”) is a fibrous sheet capable ofbeing suitably used not only as a general bandage but also as a medicalarticle such as a compression bandage used for hemostasis, compressiontherapy, and so on. The fibrous sheet has a rectangular sheet shapehaving a length direction and a width direction such as a tape shape ora belt shape (long shape).

The fibrous sheet has a bending resistance in the width direction ofless than or equal to 300 mN/200 mm, preferably less than or equal to290 mN/200 mm, more preferably less than or equal to 280 mN/200 mm. Whena fibrous sheet having a bending resistance in the width direction ofless than or equal to 300 mN/200 mm is, for example, wrapped such thatits length direction is the wrapping direction, even in the case wherethe fibrous sheet is wrapped around a site having surface protrusionsand recesses (for example, a portion located at a joint part or the likeand protruded by a bone inherent in the joint part or the like) withmoderate strength, the fibrous sheet can be wrapped along the shape ofthe surface protrusions and recesses, and is excellent in concavo-convexfitting property. From the viewpoint of the strength of the fibroussheet, the bending resistance in the width direction is usually greaterthan or equal to 30 mN/200 mm and preferably greater than or equal to 50mN/200 mm.

The phrase “wrapped such that the length direction is the wrappingdirection” is a usual mode when a long object such as a bandage iswrapped around an object to be wrapped. The case where the object to bewrapped is a finger is exemplified, a long bandage is wrapped around thefinger such that the width direction of the bandage and the lengthdirection of the finger are parallel or approximately parallel to eachother.

Conventionally, there has been known a bandage to which stretchabilityhas been imparted in the length direction by various methods; however,as a result of a study made by the present inventors, it has been foundthat even when the stretchability in the length direction is increasedor only the stretchability in the length direction is increased, theconcavo-convex fitting property cannot be satisfactorily improved. Onthe other hand, the present invention is based on the knowledge thatattention is paid in the width direction rather than the lengthdirection, and the bending resistance in the width directionunexpectedly becomes an important factor for improving theconcavo-convex fitting property.

To reduce the bending resistance in the width direction such that thebending resistance falls within the above range, and meanwhile to makethe bending resistance in the length direction larger than the bendingresistance in the width direction are effective for achieving a goodbalance between the concavo-convex fitting property and the strength,consequently the durability of the fibrous sheet. A difference inbending resistance between the length direction and the width directionis, for example, greater than or equal to 10 mN/200 mm, preferablygreater than or equal to 30 mN/200 mm, more preferably greater than orequal to 50 mN/200 mm. The fibrous sheet has a bending resistance in thelength direction of, for example, 40 to 400 mN/200 mm, preferably 60 to300 mN/200 mm.

The bending resistance of the fibrous sheet is measured according to theHandle-o-Meter method specified in JIS L 1913. According to the JISstandard, a sample having a width of 200 mm is used.

The fibrous sheet has a compression elastic modulus Pe of preferablyless than or equal to 85%, more preferably less than or equal to 80%.When the compression elastic modulus Pe is within this range, it isadvantageous for enhancing the concavo-convex fitting property. A lowerlimit of the compression elastic modulus Pe is not particularly limited,and is, for example, 50%. The compression elastic modulus Pe iscalculated in accordance with the “Test methods for nonwovens” specifiedin JIS L 1913 by the following formula [C]:

Pe={(T ₁ ′−T)/(T ₁ −T)}×100  [C].

T₁ is the thickness [mm] when an initial load (0.5 kPa) is applied. T isthe thickness [mm] when a load of 30 kPa is applied. T₁′ is thethickness [mm] when the initial load is restored.

When the fibrous sheet has extensibility, the functionality can beimproved when the fibrous sheet is used as, for example, a bandage. Byimparting extensibility to the fibrous sheet, the fixing force can beenhanced for example when the fibrous sheet is used for fixing aprotective member such as a gauze to an application site. Alternatively,when the fibrous sheet is used for imparting a compression force to anapplication site by wrapping the fibrous sheet, the compression forcecan be enhanced. In the case where the fibrous sheet havingextensibility is applied to a site to be bent and stretched, such as ajoint part, the bending and stretching motion becomes easy. The fibroussheet having extensibility is further advantageous for improvement ofthe concavo-convex fitting property.

From the above point of view, the fibrous sheet preferably hasextensibility. As described above, in the present specification,“extensible/having extensibility” means that a stress at 50% extensionis exhibited in at least one direction (first direction) in the sheetplane. The stress at 50% extension is a stress at extension at the timeof extension at 50% elongation (immediately after extension) and ismeasured by a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913.

From the viewpoint of the concavo-convex fitting property and theeasiness of the bending and stretching motion, it is preferable that thefibrous sheet has good extensibility at least in the width direction asthe first direction. This width direction may be a direction orthogonalto a flow direction (MID direction) of the fibrous sheet in a productionprocess, that is, a CD direction. A stress at 50% extension in thelateral direction of the fibrous sheet is preferably 0.1 to 20 N/50 mm,more preferably 0.5 to 15 N/50 mm, further preferably 1 to 12 N/50 mm.

On the other hand, it is preferable that the fibrous sheet has goodextensibility in the length direction in order to enhance the fixingforce and compression force of the fibrous sheet. A stress at 50%extension in the length direction of the fibrous sheet is preferably 0.1to 50 N/50 mm, more preferably 0.5 to 30 N/50 mm, further preferably 1to 20 N/50 mm. To increase the stress at 50% extension in the lengthdirection is also advantageous for improvement of the concavo-convexfitting property. The length direction of the fibrous sheet may be aflow direction (MD direction) of the fibrous sheet in a productionprocess. A stress at 50% extension in each direction other than thewidth direction and the length direction is preferably 0.5 to 60 N/50mm, more preferably 1 to 45 N/50 mm, further preferably 2 to 40 N/50 mm.

The fibrous sheet preferably exhibits self-adhesiveness. As describedabove, in the present specification, the “self-adhesiveness” refers to aproperty allowing fibers on a fibrous sheet surface to engage with eachother or come into close contact with each other due to superposition(contact) of the fibers and to be hooked or fixed. The fibrous sheethaving self-adhesiveness is advantageous when the fibrous sheet is abandage or the like. For example, in the case where the fibrous sheet isa bandage, after the bandage is wrapped around an application site, thewrapped fibrous sheets are pressed against each other while beingextended by such an operation that an end of the bandage is overlappedon (or torn and then overlapped on) a bandage surface located under theend, so that the fibrous sheets are joined and fixed to each other,thereby expressing self-adhesiveness.

When the fibrous sheet itself has self-adhesiveness, it is unnecessaryto form a layer formed of a self-adhesive agent such as an elastomer ora pressure-sensitive adhesive on a surface of the fibrous sheet or toprepare separately a fastener for fixing the tip after wrapping. Forexample, Japanese Patent Laying-Open No. 2005-095381 (PTD 4) describesthat an acrylic polymer (claim 1) or a latex (paragraphs [0004] to[0006]) is caused to adhere as a self-adhesive agent to at least oneside of a bandage base material. Formation of a layer formed of anelastomer such as latex on the fibrous sheet surface is effective forenhancing self-adhesiveness.

However, it is preferable that the fibrous sheet according to thepresent embodiment is constituted only of a nonelastomer material. Morespecifically, it is preferable that the fibrous sheet is constitutedonly of fibers. When the layer formed of an elastomer as described aboveis formed on the fibrous sheet surface or the elastomer is impregnatedinto a fiber base material, it tends to be relatively difficult to setthe bending resistance in the width direction to the above range. Thelayer formed of an elastomer may induce skin irritation and allergy whenwrapped around an application site.

The self-adhesiveness of the fibrous sheet can be evaluated by a curvedsurface sliding stress. From the viewpoint of the self-adhesiveness, itis preferable that the fibrous sheet has a curved surface sliding stressof, for example, greater than or equal to 3 N/50 mm, preferably greaterthan or equal to 5 N/50 mm, and the curved surface sliding stress ispreferably higher than breaking strength. Since it is relatively easy tounwrap the wrapped fibrous sheet if desired, the curved surface slidingstress is preferably less than or equal to 30 N/50 mm, more preferablyless than or equal to 25 N/50 mm. The curved surface sliding stress ismeasured using a tensile tester in accordance with the method describedin Examples section (FIGS. 1 to 3).

The fibrous sheet preferably has a hand cut property. As describedabove, in the present specification, the “hand cut property” refers to aproperty enabling breakage (cutting) by hand tension. The hand cutproperty of the fibrous sheet can be evaluated by breaking strength.From the viewpoint of the hand cut property, the fibrous sheet has abreaking strength in at least one direction in the sheet plane ofpreferably 5 to 100 N/50 mm, more preferably 8 to 60 N/50 mm, furtherpreferably 10 to 40 N/50 mm. When the breaking strength is within theabove range, it is possible to impart a good hand cut property enablingrelatively easy breakage (cutting) by hand. If the breaking strength istoo large, the hand cut property deteriorates, making it difficult tocut the fibrous sheet with one hand, for example. On the other hand, ifthe breaking strength is too small, the strength of the fibrous sheetbecomes insufficient to cause easy breakage of the fibrous sheet, anddurability and handleability are lowered. The breaking strength ismeasured by a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913.

At least one direction in the sheet plane is a tensile direction whenthe fibrous sheet is cut by hand, and is preferably the lengthdirection. The length direction may be the MD direction. That is, whenthe fibrous sheet is used as a bandage, it is usual to break the bandagein the length direction after the bandage is wrapped around anapplication site while being extended along the length directionthereof, and therefore the direction where the breaking strength iswithin the above range is preferably the length direction as the tensiledirection.

The breaking strength in a direction other than at least one directionin the sheet plane, for example, the width direction or the CD directionis, for example, 0.1 to 300 N/50 mm, preferably 0.5 to 100 N/50 mm, morepreferably 1 to 20 N/50 mm.

From the viewpoint of the hand cut property, it is preferable that thefibrous sheet is constituted only of a non-elastomer material. Morespecifically, it is preferable that the fibrous sheet is constitutedonly of fibers. If a layer formed of an elastomer, etc. is formed on thefibrous sheet surface, the hand cut property may be lowered.

The fibrous sheet has an elongation at break in at least one directionin the sheet plane of, for example, greater than or equal to 50%,preferably greater than or equal to 60%, more preferably greater than orequal to 80%. When the elongation at break is within the above range, itis advantageous for enhancing the stretchability of the fibrous sheet.The elongation at break in at least one direction in the sheet plane isusually less than or equal to 300% and preferably less than or equal to250%. The elongation at break is also measured by a tensile test inaccordance with the “Test methods for nonwovens” specified in JIS L1913.

From the viewpoint of the concavo-convex fitting property and theeasiness of the bending and stretching motion, at least one direction inthe sheet plane is preferably the width direction. From the viewpoint ofextensibility in the length direction (for example, from the viewpointof the fixing force and the compression force described above), at leastone direction in the sheet plane is preferably the length direction. Theelongation at break in a direction other than at least one direction inthe sheet plane is, for example, 10 to 500%, preferably 100 to 350%.

The fibrous sheet has a recovery rate after 50% extension in at leastone direction in the sheet plane (recovery rate after 50% extension) ispreferably greater than or equal to 70% (less than or equal to 100%),more preferably greater than or equal to 80%, further preferably greaterthan or equal to 90%. When the fibrous sheet having a recovery rateafter 50% extension within the range is wrapped around a site havingsurface protrusions and recesses, such as a joint part, or a site to bebent and stretched, the fibrous sheet is easy to follow the shape of thesurface protrusions and recesses of the site and the bending andstretching motion. It is advantageous for improvement of theconcavo-convex fitting property and the easiness of the bending andstretching motion, and also advantageous for improvement of theself-adhesiveness due to friction between the overlapped fibrous sheets.If the extension recovery rate is excessively small, the fibrous sheetcannot follow the bending motion of the site, and deformation of thefibrous sheet caused by this motion does not return to its originalshape, thus weakening fixation of the wrapped fibrous sheet.

From the viewpoint of the concavo-convex fitting property and theeasiness of the bending and stretching motion, at least one direction inthe sheet plane is preferably the width direction. From the viewpoint ofextensibility in the length direction (for example, from the viewpointof the fixing force and the compression force described above), at leastone direction in the sheet plane is preferably the length direction. Therecovery rate after 50% extension is defined by the following formula:

Recovery rate after 50% extension (%)=100−X

when, in a tensile test in accordance with the “Test methods fornonwovens” specified in JIS L 1913, a residual strain (%) after the testis defined as X when load is removed immediately after the elongationrate reaches 50%.

The recovery rate after 50% extension in a direction other than at leastone direction in the sheet plane is, for example, greater than or equalto 70% (less than or equal to 100%), preferably greater than or equal to80%.

The fibrous sheet has a basis weight of preferably 30 to 300 g/m², morepreferably 50 to 200 g/m². In order to further improve theconcavo-convex fitting property, the basis weight is preferably small,and in this case, the basis weight is preferably less than or equal to160 g/m². If the basis weight is excessively small, the strength,consequently the durability of the fibrous sheet is lowered.

The fibrous sheet has a thickness of, for example, 0.2 to 5 mm,preferably 0.3 to 3 mm, more preferably 0.4 to 2 mm. When the basisweight and the thickness are within these ranges, a balance among theconcavo-convex fitting property, the ease of bending exhibited whenwrapping the fibrous sheet, the extensibility, flexibility, touchfeeling and cushioning property of the fibrous sheet is good. A density(bulk density) of the fibrous sheet can be a value corresponding to theabove-described basis weight and thickness, and the density (bulkdensity) is, for example, 0.03 to 0.5 g/cm³, preferably 0.04 to 0.4g/cm³, more preferably 0.05 to 0.25 g/cm³. From the viewpoint of furtherimproving the concavo-convex fitting property, the density is morepreferably less than or equal to 0.2 g/cm³.

The fibrous sheet has an air permeability measured by the Frazier methodof preferably greater than or equal to 0.1 cm³/(cm²·second), morepreferably 1 to 500 cm³/(cm²·second), further preferably 5 to 300cm³/(cm²·second), particularly preferably 10 to 200 cm³/(cm²·second).When the air permeability is within this range, the fibrous sheet ismore suitably used for the human body, such as a bandage, because thefibrous sheet is good in air permeability and is hardly stuffy.

(2) Structure and Production Method of Fibrous Sheet

The fibrous sheet of the present embodiment is not particularly limitedas long as it is constituted of fibers, and the fibrous sheet may be,for example, a woven fabric, a nonwoven fabric, a knit (knitted fabric),or the like. As described above, the fibrous sheet has a rectangularsheet shape having a length direction and a width direction such as atape shape or a belt shape (long shape). The fibrous sheet may have asingle layer structure or a multilayer structure including two or morefibrous layers.

As described above, the fibrous sheet preferably has extensibility.Examples of means for imparting stretchability and extensibility to thefibrous sheet may include 1) a method of subjecting a fibrous sheetsubstrate such as a woven fabric, a nonwoven fabric, or a knit togathering; 2) a method of weaving, into a fibrous sheet, yarn formed ofa stretchable material such as an elastomer typified by rubber; 3) amethod of combining a layer formed of a stretchable material such as anelastomer with a nonstretchable fibrous sheet substrate or impregnatinga nonstretchable fibrous sheet substrate with a stretchable material; 4)a method using crimped fibers crimped into a coil shape as at least somefibers constituting a nonwoven fabric; and the like.

Among the above methods, the fibrous sheet according to the presentembodiment is preferably obtained by using the method described in 4).Although the gathering described in 1) is effective in thatstretchability can be effectively imparted to the fibrous sheet, it isrelatively difficult to obtain a fibrous sheet in which the bendingresistance in the width direction is within the above range depending onthe wavy shape of the gather. According to the methods 2) and 3), whilestretchability can be easily imparted to the fibrous sheet, flexibilityis lost, and it is relatively difficult to obtain a fibrous sheet inwhich the bending resistance in the width direction is within the aboverange.

From the viewpoint of concavo-convex fitting property, ease of bendingof a joint part exhibited when the fibrous sheet is wrapped around thejoint part, self-adhesiveness, hand cut property, etc., the fibroussheet is preferably constituted of a nonwoven fabric, namely, thefibrous sheet is preferably a nonwoven fabric sheet. More preferably,the fibrous sheet is constituted of a nonwoven fabric containing crimpedfibers crimped into a coil shape, and still more preferably, the fibroussheet is constituted of a nonwoven fabric that contains the crimpedfibers and that is not subjected to at least one of treatments(desirably all treatments) described in 1) to 3). Particularlypreferably, the nonwoven fabric sheet is constituted only of the crimpedfibers. Although the fibrous sheet may be constituted of a woven fabricor a knit (knitted fabric), the fineness of yarn (twisted yarn)constituting a woven fabric or a knit (knitted fabric) is relativelylarge, so that it is relatively difficult to obtain a fibrous sheethaving bending resistance in the width direction within the above range.In this regard, when a nonwoven fabric is used, a sheet can beconstituted of fibers with smaller fineness, and the concavo-convexfitting property can be further improved.

From the viewpoint of the concavo-convex fitting property, an averagefineness of fibers constituting a sheet formed of a nonwoven fabric ispreferably less than or equal to 20 dtex, more preferably less than orequal to 15 dtex. The average fineness is preferably greater than orequal to 0.5 dtex, more preferably greater than or equal to 1.0 dtex,from the viewpoint of the strength, consequently the durability of thefibrous sheet.

It is preferable that the fibrous sheet constituted of the nonwovenfabric containing the crimped fibers has a structure in which therespective fibers constituting this nonwoven fabric are notsubstantially fusion-bonded, but mainly the crimped fibers are entangledwith each other at their crimped coil portions and bound or hooked.Further, it is preferable that most (the majority of) crimped fibers(axial direction of crimped fibers) are oriented substantially parallelto a sheet surface. As described above, in the present specification,“oriented substantially parallel to a surface direction” means a statewhere a portion in which a large number of crimped fibers (axialdirection of crimped fibers) are locally oriented along a thicknessdirection is not repeatedly present, as in for example entanglement byneedle punching.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, the crimped fibers are preferably oriented in a certaindirection in the sheet plane (preferably in the length direction), andthe adjacent or intersecting crimped fibers are entangled with eachother at their crimped coil portions. Even in the thickness direction(or oblique direction) of the fibrous sheet, the crimped fibers arepreferably slightly entangled with each other. The entanglement of thecrimped fibers can be caused by the process of shrinking a fibrous webas a precursor of the fibrous sheet.

The nonwoven fabric in which crimped fibers (axial direction of crimpedfibers) are oriented in a certain direction in the sheet plane andentangled exhibits good stretchability (including extensibility) in thisdirection. In the case where the certain direction is, for example, thelength direction, when a tensile force is applied to the stretchablenonwoven fabric in the length direction, the entangled crimped coilportion tends to extend and return to the original coil shape, so thathigh stretchability can be exhibited in the length direction. Thisstretchable nonwoven fabric can exhibit excellent extensibility in adirection (for example, the width direction) orthogonal to the certaindirection in the sheet plane. The cushioning property and flexibility inthe thickness direction can be expressed by slight entanglement of thecrimped fibers in the thickness direction of the nonwoven fabric,whereby the nonwoven fabric can have good touch feeling and texture. Thecrimped coil portion easily entangles with another crimped coil portionby contact with a certain degree of pressure. The self-adhesiveness canbe expressed by the entanglement of the crimped coil portions.

In the fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers, when a tensile force is applied to the orientationdirection of the crimped fiber (preferably in the length direction), theentangled crimped coil portion extends due to elastic deformation, andwhen the tensile force is further applied, the fibrous sheet is finallyunwrapped, so that the cutting property (hand cut property) is alsogood.

As described above, the nonwoven fabric capable of constituting thefibrous sheet preferably contains crimped fibers crimped into a coilshape. The crimped fiber is preferably oriented mainly in the surfacedirection of the nonwoven fabric, and further preferably crimpssubstantially evenly in the thickness direction. The crimped fiber canbe constituted of a conjugated fiber in which a plurality of resinshaving different thermal shrinkage factors (or thermal expansioncoefficients) form a phase structure.

The conjugated fiber constituting the crimped fiber is a fiber (latentlycrimped fiber) having an asymmetric or layered (so-called bimetal)structure crimped by heating due to a difference in thermal shrinkagefactor (or thermal expansion coefficient) of a plurality of resins. Theplurality of resins usually have mutually different softening points ormelting points. The plurality of resins can be selected fromthermoplastic resins such as, for example, polyolefin-based resins(e.g., poly-C₂₋₄ olefin-based resins such as low-density, medium-densityor high-density polyethylene and polypropylene); acrylic resins (e.g.,acrylonitrile-based resins having an acrylonitrile unit, such asacrylonitrile-vinyl chloride copolymers); polyvinyl acetal-based resins(e.g., polyvinyl acetal resins); polyvinyl chloride-based resins (e.g.,polyvinyl chloride, vinyl chloride-vinyl acetate copolymers and vinylchloride-acrylonitrile copolymers); polyvinylidene chloride-based resins(e.g., vinylidene chloride-vinyl chloride copolymers and vinylidenechloride-vinyl acetate copolymers); styrene-based resins (e.g.,heat-resistant polystyrene); polyester-based resins (e.g., poly-C₂₋₄alkylene arylate-based resins such as polyethylene terephthalate resins,polytrimethylene terephthalate resins, polybutylene terephthalate resinsand polyethylene naphthalate resins); polyamide-based resins (e.g.,aliphatic polyamide-based resins such as polyamide 6, polyamide 66,polyamide 11, polyamide 12, polyamide 610 and polyamide 612,semi-aromatic polyamide-based resins, and aromatic polyamide-basedresins such as polyphenylene isophthalamide, polyhexamethyleneterephthalamide and poly-p-phenyleneterephthalamide);polycarbonate-based resins (e.g., bisphenol A-type polycarbonate);polyparaphenylene benzobisoxazole resins; polyphenylene sulfide resins;polyurethane-based resins; and cellulose-based resins (e.g., celluloseesters). These thermoplastic resins may contain other copolymerizableunits.

Among the thermoplastic resins, non thermal adhesive resins undermoisture (or heat-resistant hydrophobic resins or nonaqueous resins)having a softening point or melting point greater than or equal to 100°C., such as, for example, polypropylene-based resins, polyester-basedresins and polyamide-based resins are preferable because fibers are notmelted or softened to be fused even when subjected to a heatingtreatment with high-temperature steam. Particularly, aromaticpolyester-based resins and polyamide-based resins are preferable becausethey are excellent in balance among heat resistance, fiber formability,and so on. A resin exposed to surfaces of conjugated fibers constitutinga nonwoven fabric (latently crimped fiber) is preferably at least a nonthermal adhesive resin under moisture so that the conjugated fibers arenot fused even when treated with high-temperature steam.

The plurality of resins forming the conjugated fiber may have differentthermal shrinkage factors, and may be a combination of resins of thesame kind, or a combination of different kinds of resins.

Preferably, the plurality of resins forming the conjugated fiber are acombination of resins of the same kind from the viewpoint ofadhesiveness. In the case of the combination of resins of the same kind,usually a combination of a component (A) forming a homopolymer(essential component) and a component (B) forming a modification polymer(copolymer) is used. That is, for example, a copolymerizable monomer forreducing the crystallization degree, the melting point, the softeningpoint, or the like is copolymerized with the homopolymer as an essentialcomponent to perform modification, whereby the crystallization degreemay be reduced as compared to the homopolymer, or the polymer may bemade noncrystalline to reduce the melting point or softening point ascompared to the homopolymer. When the crystallization degree, themelting point, or the softening point is changed as described above,this can cause a difference in thermal shrinkage factor. The differencein melting point or softening point is, for example, 5 to 150° C., andpreferably 40 to 130° C., more preferably 60 to 120° C. A ratio of thecopolymerizable monomer to be used for modification is, for example, 1to 50 mol %, preferably 2 to 40 mol %, more preferably 3 to 30 mol %(particularly 5 to 20 mol %) based on the whole amount of monomers.While a mass ratio between the component forming a homopolymer and thecomponent forming a modification polymer can be selected according tothe structure of fibers, the homopolymer component (A)/the modificationpolymer component (B) is for example 90/10 to 10/90, and preferably70/30 to 30/70, more preferably 60/40 to 40/60.

The conjugated fiber is preferably a combination of aromaticpolyester-based resins, more preferably a combination of a polyalkylenearylate-based resin (a) and a modified polyalkylene arylate-based resin(b) because latently crimpable conjugated fibers are easily produced.The polyalkylene arylate-based resin (a) can be a homopolymer of anaromatic dicarboxylic acid (e.g., a symmetric aromatic dicarboxylic acidsuch as terephthalic acid or naphthalene-2,6-dicarboxylic acid) and analkanediol component (e.g., C₂₋₆ alkanediol such as ethylene glycol orbutylene glycol). Specifically, a poly-C₂₋₄ alkylene terephthalate-basedresin such as polyethylene terephthalate (PET) or polybutyleneterephthalate (PBT), or the like is used, and usually, PET for use ingeneral PET fibers having an intrinsic viscosity of 0.6 to 0.7 is used.

On the other hand, in the modified polyalkylene arylate-based resin (b),examples of a copolymerization component for reducing the melting pointor softening point and the crystallization degree of the polyalkylenearylate-based resin (a) as an essential component include dicarboxylicacid components such as an asymmetric aromatic dicarboxylic acid, analicyclic dicarboxylic acid and an aliphatic dicarboxylic acid; analkanediol component having a chain length longer than that ofalkanediol of the polyalkylene arylate-based resin (a); and/or an etherbond-containing diol component. The copolymerization components may beused singly, or in combination of two or more kinds thereof. Among thesecomponents, as the dicarboxylic acid component, asymmetric aromaticdicarboxylic acids (e.g., isophthalic acid, phthalic acid and 5-sodiumsulfoisophthalic acid), aliphatic dicarboxylic acids (C₆₋₁₂ aliphaticdicarboxylic acids such as adipic acid), or the like are generally used.As the diol component, alkanediols (e.g., C₃₋₆ alkanediols such as1,3-propanediol, 1,4-butanediol, 1,6-hexanediol and neopentyl glycol),polyoxyalkylene glycols (e.g., polyoxy-C₂₋₄ alkylene glycols such asdiethylene glycol, triethylene glycol, polyethylene glycol andpolytetramethylene glycol) or the like are generally used. Among them,asymmetric aromatic dicarboxylic acids such as isophthalic acid, andpolyoxy-C₂₋₄ alkylene glycols such as diethylene glycol are preferable.The modified polyalkylene arylate-based resin (b) may be an elastomerhaving a C₂₋₄ alkylene arylate (e.g., ethylene terephthalate or butyleneterephthalate) as a hard segment and a polyoxyalkylene glycol or thelike as a soft segment.

In the modified polyalkylene arylate-based resin (b), a ratio of thedicarboxylic acid component (e.g., isophthalic acid) for reducing themelting point or softening point is, for example, 1 to 50 mol %,preferably 5 to 50 mol %, more preferably 15 to 40 mol % based on thewhole amount of dicarboxylic acid components constituting the modifiedpolyalkylene arylate-based resin (b). A ratio of the diol component(e.g., diethylene glycol) for reducing the melting point or softeningpoint is, for example, less than or equal to 30 mol %, preferably lessthan or equal to 10 mol % (e.g., 0.1 to 10 mol %) based on the wholeamount of diol components constituting the modified polyalkylenearylate-based resin (b). If the ratio of copolymerization components istoo low, sufficient crimps are not expressed, and thus the formstability and stretchability of the nonwoven fabric after expression ofcrimps are lowered. On the other hand, if the ratio of copolymerizablecomponents is too high, although crimp expressing performance isimproved, it is difficult to stably perform spinning.

The modified polyalkylene arylate-based resin (b) may include, asmonomer components, polyvalent carboxylic acid components such astrimellitic acid and pyromellitic acid, polyol components such asglycerol, trimethylolpropane, trimethylolethane and pentaerythritol, andso on as necessary.

A transverse cross-sectional shape of the conjugated fiber(cross-sectional shape perpendicular to the longitudinal direction ofthe fiber) is not limited to a general solid cross-sectional shape suchas a circular cross-sectional shape or an irregular cross-sectionalshape [flat shape, elliptical shape, polygonal shape, 3 to 14-foliatedshape, T-shape, H-shape, V-shape, dog-bone (I-shape) or the like], andit may be a hollow cross-sectional shape or the like. Usually, thetransverse cross-sectional shape of the conjugated fiber is a circularcross-sectional shape.

Examples of the transverse cross-sectional structure of the conjugatedfiber include phase structures formed of a plurality of resins, such as,for example, structures of core-sheath type, sea-island type, blendtype, parallel type (side-by-side type or multilayer lamination type),radial type (radial lamination type), hollow radial type, block type,random composite type and the like. In particular, a structure in whichphase parts neighbor each other (so-called bimetal structure), and astructure in which a phase structure is asymmetric, such as, forexample, a structure of eccentric core-sheath type or parallel type arepreferable because spontaneous crimps are easily expressed by heating.

In the case where the conjugated fiber has a structure of core-sheathtype such as a structure of eccentric core-sheath type, the core partmay be made from a thermal adhesive resin under moisture (e.g., a vinylalcohol-based polymer such as an ethylene-vinyl alcohol copolymer orpolyvinyl alcohol), or a thermoplastic resin having a low melting pointor softening point (e.g., polystyrene or low-density polyethylene) aslong as there is a difference in thermal shrinkage with the non thermaladhesive resin under moisture of the sheath part situated at thesurface, and thus the fiber can be crimped.

The conjugated fibers have an average fineness of, for example, 0.1 to20 dtex, preferably 0.5 to 10 dtex, more preferably 1 to 5 dtex. If thefineness is too small, it is difficult to produce fibers themselves,and, in addition, it is difficult to secure fiber strength. Further, itis difficult to express fine coil-shaped crimps in a process ofexpressing crimps. On the other hand, if the fineness is too large, itbecomes difficult to adjust the bending resistance in the widthdirection to the above range, and in addition, it becomes difficult toexpress sufficient crimps.

The conjugated fibers have an average fiber length of, for example, 10to 100 mm, and preferably 20 to 80 mm, more preferably 25 to 75 mm. Ifthe average fiber length is too short, it is difficult to form a fiberweb, and, in addition, entanglement of crimped fibers is insufficientwhen crimps are expressed, so that it may be difficult to secure thestrength and stretchability of the nonwoven fabric. If the average fiberlength is too long, it is difficult to form a fiber web with a uniformbasis weight, and further, a large number of entanglements of fibers areexpressed at the time of forming the web, so that fibers may obstructone another at the time of expressing crimps, resulting in difficulty inexpression of stretchability. When the average fiber length is withinthe above range, some fibers crimped on the nonwoven fabric surface areappropriately exposed on the nonwoven fabric surface, so that theself-adhesiveness of the nonwoven fabric can be improved. The averagefiber length within the above range is advantageous for obtaining goodhand cut property.

The above-described conjugated fiber is a latently crimped fiber, andwhen the conjugated fibers are heat-treated, crimps are expressed (orappear), and thus the conjugated fibers are fibers having substantiallycoil-shaped (helical or spiral spring-shaped) three-dimensional crimps.

The number of crimps (number of mechanical crimps) before heating is,for example, 0 to 30 crimps/25 mm, preferably 1 to 25 crimps/25 mm, morepreferably 5 to 20 crimps/25 mm. The number of crimps after heating is,for example, greater than or equal to 30 crimps/25 mm (for example 30 to200 crimps/25 mm), and preferably 35 to 150 crimps/25 mm.

As described above, the crimped fibers constituting the nonwoven fabrichave substantially coil-shaped crimps after expression of crimps. Anaverage curvature radius of circles formed by the coils of the crimpedfibers is, for example, 10 to 250 μm, and preferably 20 to 200 morepreferably 50 to 160 μm. The average curvature radius is an indexexpressing an average size of circles formed by the coils of crimpedfibers, and in the case where this value is large, the formed coil has aloose shape, i.e., a shape having a small number of crimps. If thenumber of crimps is small, the number of entanglements of crimped fibersalso decreases, and it is difficult to recover the shape againstdeformation of the coil shape, so that it is disadvantageous forexpressing sufficient stretching performance. If the average curvatureradius is too small, crimped fibers are not satisfactorily entangledwith each other, so that it is difficult to secure web strength.Further, when the coil shape is deformed, stress is too large andbreaking strength is excessively increased, so that it is difficult toobtain suitable stretchability.

In the crimped fibers, an average pitch (average crimp pitch) of thecoil is, for example, 0.03 to 0.5 mm, preferably 0.03 to 0.3 mm, morepreferably 0.05 to 0.2 mm. If the average pitch is excessively large,the number of coil crimps that can be expressed per fiber decreases, sothat sufficient stretchability cannot be exhibited. If the average pitchis excessively small, crimped fibers are not satisfactorily entangledwith each other, so that it becomes difficult to secure the strength ofthe nonwoven fabric.

The nonwoven fabric (fibrous web) may contain other fibers(non-conjugated fibers) in addition to the above-described conjugatedfibers. Specific examples of the non-conjugated fiber include, inaddition to fibers constituted of the above-described non thermaladhesive resin under moisture or thermal adhesive resin under moisture,fibers constituted of cellulose-based fibers [e.g., natural fibers(e.g., cotton, wool, silk, and hemp), semi-synthetic fibers (e.g.,acetate fibers such as triacetate fibers), and regenerated fibers (e.g.,rayon, polynosic, cupra, and lyocell (e.g., registered trademark“Tencel”))] and the like. An average fineness and average fiber lengthof the non-conjugated fibers can be the same as those of the conjugatedfibers. The non-conjugated fibers may be used singly, or in combinationof two or more kinds thereof.

A ratio (mass ratio) of the conjugated fiber and the non-conjugatedfiber is preferably adjusted appropriately so that the bendingresistance in the width direction falls within the above-describedrange. As the ratio, the conjugated fiber/the non-conjugated fiber is,for example, 50/50 to 100/0, and preferably 60/40 to 100/0, morepreferably 70/30 to 100/0, still more preferably 80/20 to 100/0,particularly preferably 90/10 to 100/0. A balance between the strengthand stretchability or flexibility of the nonwoven fabric can be adjustedby blending the non-conjugated fibers.

The nonwoven fabric (fibrous web) may contain commonly used additives,such as stabilizers (e.g., thermal stabilizers, ultraviolet absorbers,light stabilizers, and antioxidants), antibacterial agents, deodorants,fragrances, colorants (dyes and pigments), fillers, antistatic agents,flame retardants, plasticizers, lubricants, and crystallization speedretardants. The additives may be used singly, or in combination of twoor more kinds thereof. The additive may be supported to the fibersurface or may be contained in the fiber.

The fibrous sheet constituted of the nonwoven fabric containing thecrimped fibers can be suitably produced by a method including a step(web formation step) of forming fibers containing the above-describedconjugated fibers (latently crimped fibers) into a web and a step(heating step) of heating the fibrous web and crimping the conjugatedfibers.

As a method of forming the fibrous web in the web formation step, it ispossible to use a commonly used method such as a direct method includinga spunbond method or a melt-blow method, a carding method usingmelt-blow fibers, staple fibers, or the like, or a dry method such as anair-lay method. Among them, a carding method using melt-blow fibers orstaple fibers, particularly, a carding method using staple fibers iscommonly used. Examples of the web obtained by using staple fibersinclude a random web, a semi-random web, a parallel web, and across-wrap web.

Prior to the heating step, an entangling step of entangling at leastsome fibers in the fibrous web may be carried out. A nonwoven fabric inwhich crimped fibers are suitably entangled can be obtained in the nextheating step by carrying out the entangling step. Although theentangling method may be a method of mechanically performingentanglement, preferred is a method of performing entanglement byspraying or injecting (blowing) water. The entanglement of the fiberswith water flow is advantageous in increasing the density of theentanglement by crimping in the heating step. Although the water to besprayed or injected may be blown from one or both sides of the fibrousweb, it is preferable to blow water from both sides from the viewpointof efficiently performing strong entanglement.

A jetting pressure of water in the entangling step is, for example,greater than or equal to 2 MPa, preferably 3 to 12 MPa, more preferably4 to 10 MPa, so that the fiber entanglement falls within an appropriaterange. A temperature of the sprayed or injected water is, for example, 5to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water, preferred is a method ofinjecting water with use a nozzle or the like having a regular sprayarea or spray pattern, from the viewpoint of convenience and the like.Specifically, water can be injected onto a fibrous web transferred by abelt conveyor such as an endless conveyor, while the fibrous web isplaced on a conveyor belt. The conveyor belt may be water-permeable, andwater may pass through the water-permeable conveyor belt from the backside of the fibrous web to be injected onto the fibrous web. In order tosuppress scattering of fibers due to water injecting, the fibrous webmay be wetted with a small amount of water in advance.

As the nozzle for spraying or injecting water, a plate or die havingpredetermined orifices successively arranged in a width directionthereof is used, and the plate or die may be disposed to arrange theorifices in the width direction of the fibrous web to be conveyed. Thenumber of orifice lines may be at least one, and a plurality of orificelines may be arranged in parallel. A plurality of nozzle dies eachhaving one orifice line may be installed in parallel.

Prior to the entangling step, a step (uneven distribution step) ofunevenly distributing the fibers in the fibrous web in the plane may beprovided. When this step is carried out, a region where fiber densitybecomes sparse is formed in the fibrous web, and therefore, in the casewhere the entangling step is water flow entanglement, a water flow canbe efficiently injected into the fibrous web, so that moderateentanglement can be easily realized not only on a surface of the fibrousweb but also inside thereof.

The uneven distribution step can be performed by spraying or injectinglow-pressure water onto the fibrous web. The low-pressure water may besuccessively sprayed or injected onto the fibrous web, but it ispreferable that the low-pressure water is intermittently or periodicallysprayed onto the fibrous web. When water is intermittently orperiodically sprayed onto the fibrous web, it is possible toperiodically and alternately form a plurality of low-density portionsand a plurality of high-density portions.

It is desirable that a jetting pressure of water in the unevendistribution step is as low as possible, and the jetting pressure ofwater is, for example, 0.1 to 1.5 MPa, preferably 0.3 to 1.2 MPa, morepreferably 0.6 to 1.0 MPa. A temperature of the sprayed or injectedwater is, for example, 5 to 50° C., and preferably 10 to 40° C.

As a method of spraying or injecting water intermittently orperiodically, there is no particular limitation as long as it is amethod capable of periodically and alternately forming a gradient ofdensity on the fibrous web; however, from the viewpoint of convenienceand the like, preferred is a method of injecting water through aplate-like object (e.g., porous plate) having a regular spray area orspray pattern formed with a plurality of holes.

In the heating step, the fibrous web is heated with high temperaturesteam and crimped. In the method of treating the fibrous web with hightemperature steam, the fibrous web is exposed to a high temperature orsuperheated steam (high pressure steam) flow, whereby coil crimps occurin the conjugated fibers (latently crimped fibers). The fibrous web hasair permeability. Accordingly, high temperature steam permeates into thefibrous web even in treatment from one direction, substantially uniformcrimps are expressed in the thickness direction, and the fibers areuniformly entangled with each other.

The fibrous web shrinks simultaneously with high temperature steamtreatment. Accordingly, it is desirable that the fibrous web to besupplied is overfed according to the area shrinkage ratio of an intendednonwoven fabric immediately before the fibrous web is exposed to hightemperature steam. A ratio of the overfeeding is 110 to 300%, preferably120 to 250%, based on the length of the intended nonwoven fabric.

In order to supply the fibrous web with steam, a commonly used steaminjecting apparatus may be used. The steam injecting apparatus ispreferably an apparatus capable of generally uniformly blowing steamover the whole width of the fibrous web with a desired pressure andamount. The steam injecting apparatus may be provided only on onesurface side of the fibrous web, or in order to treat the front and backof the fibrous web with steam at a time, the steam spraying apparatusmay be further provided on the other surface side.

Since the high temperature steam injected from the steam injectingapparatus is a gas flow, the high temperature steam enters inside thefibrous web without significantly moving the fibers in the fibrous web,unlike the water flow entanglement treatment and the needle punchingtreatment. By virtue of the entry action of the steam flow into thefibrous web, the steam flow efficiently covers a surface of each fiberexisting in the fibrous web, and enables uniform thermal crimping. Sinceheat can be satisfactorily conducted inside the fibrous web, as comparedwith the dry heat treatment, the degree of crimping is almost uniform inthe plane direction and the thickness direction.

Similarly to the nozzle for water flow entanglement, as a nozzle forinjecting high temperature steam, a plate or die having predeterminedorifices successively arranged in a width direction thereof is used, andthe plate or die may be disposed to arrange the orifices in the widthdirection of the fibrous web to be conveyed. The number of orifice linesmay be at least one, and a plurality of orifice lines may be arranged inparallel. A plurality of nozzle dies each having one orifice line may beinstalled in parallel.

A pressure of the high temperature steam to be used can be selected fromthe range of 0.1 to 2 MPa (for example, 0.2 to 1.5 MPa). If the pressureof the steam is too high, the fibers forming the fibrous web may movemore than required to cause disturbance of the texture, or the fibersmay be intermingled more than required. When the pressure is too weak,it becomes impossible to give the quantity of heat required forexpression of crimps of the fibers to the fibrous web, or the steamcannot penetrate the fibrous web and expression of crimps of the fibersin the thickness direction tends to be nonuniform. Although depending onmaterials of the fibers and the like, a temperature of the hightemperature steam can be selected from the range of 70 to 180° C. (forexample, 80 to 150° C.). A treatment speed with high temperature steamcan be selected from the range of less than or equal to 200 m/minute(for example, 0.1 to 100 m/minute).

After thus causing expression of crimps of the conjugated fiber in thefibrous web, there may be a case where water remains in the nonwovenfabric, and therefore, a drying step of drying the nonwoven may beprovided as necessary. Examples of the drying method may include amethod using a drying apparatus such as a cylinder dryer or a tenter; anon-contact method such as far infrared ray irradiation, microwaveirradiation, or electron beam irradiation; a method of blowing hot airor passing the nonwoven fabric through hot air, and the like.

Examples of a method for adjusting the bending resistance in the widthdirection to the above-described range in the method of producing afibrous sheet may include a method of adjusting a content ratio of theconjugated fibers and the non-conjugated fibers; a method of adjustingconditions of the high temperature steam (in particular, temperatureand/or pressure) used in the heating step; a method of adjusting thedrying temperature in the drying step; and the like.

EXAMPLES

Hereinafter, the present invention will be described more specificallywith reference to examples, but the present invention is not limited bythese examples. Physical property values in fibrous sheets (bandages)obtained in Examples and Comparative Examples below were measured by thefollowing methods.

[1] Number of Mechanical Crimps (Crimps/25 mm)

The number of machine crimps was measured in accordance with JIS L 1015“Chemical fiber staple test method” (8.12.1).

[2] Number of Average Coil Crimps (Coil Crimps/mm)

A crimped fiber (conjugated fiber) was removed with care from a fibroussheet so as not to stretch coil crimps, and in the same manner asmeasurement of the number of machine crimps, the number of average coilcrimps was measured in accordance with JIS L 1015 “Chemical fiber stapletest method” (8.12.1).

[3] Average Crimp Pitch (μm)

At the time of measuring the number of average coil crimps, a distancebetween successive adjacent coils was measured, and an average crimppitch was measured as an average value of n=100.

[4] Average Curvature Radius (μm)

A photograph of an arbitrary cross section of a fibrous sheet enlarged100 times was taken using a scanning electron microscope (SEM). For afiber forming a spiral (coil) of one or more rounds, among fibers in thephotograph of the cross section thus taken, the radius of a circle whenthe circle was described along the spiral (the radius of a circle when acrimped fiber was observed in a coil axial direction) was determined asa curvature radius (μm). When a fiber drew a spiral ovally, ½ of the sumof the major axis and the minor axis of the oval was determined as thecurvature radius. However, for excluding the case where sufficientcoiled crimps were not expressed in the crimped fiber, or the case wherethe spiral form of the fiber was seen as an oval because it was observeddiagonally, only ovals having a ratio between the major axis and theminor axis falling within the range of 0.8 to 1.2 were selected asobjects to be measured. An average curvature radius (m) was determinedas an average value of n=100.

[5] Basis Weight (g/m²)

A basis weight was measured in accordance with the “Test methods fornonwovens” specified in JIS L 1913.

[6] Thickness (mm) and Density (g/cm³)

In Examples and Comparative Examples (Examples 1 to 4, ComparativeExample 1) according to the first embodiment and Examples andComparative Examples (Examples 7 and 8, Comparative Examples 5 and 6)according to the third embodiment, a thickness of a fibrous sheet wasmeasured in accordance with the “Test methods for nonwovens” specifiedin JIS L 1913, and a density was calculated from this value and thebasis weight measured by the method of [5].

In Examples and Comparative Examples (Examples 5 and 6, ComparativeExamples 2 to 4) according to the second embodiment, a thickness T₁ of asingle fibrous sheet was measured in accordance with the A methodspecified in JIS L 1913 (load: 0.5 kPa). A thickness T₃ of threesuperimposed fibrous sheets was measured under the same conditions. Fromthese measured values, {T₃/(3×T₁)}×100 as the left side of the aboveformula [A] was calculated. A density (g/cm³) was calculated from thebasis weight measured by the method of [5] and the thickness T₁ measuredby the above method.

[7] Bending Resistance (mN/200 mm) in Examples and Comparative Examples(Examples 7 and 8, Comparative Examples 5 and 6) According to ThirdEmbodiment

A bending resistance was measured in accordance with the Handle-o-Metermethod in the “Test methods for nonwovens” specified in JIS L 1913. Thewidth of a measurement sample was set to 200 mm. The bending resistancewas measured for each of the length direction (MD direction) and thewidth direction (CD direction) of a fibrous sheet.

[8] Breaking Strength (N/50 mm) and Elongation at Break (%)

A basis weight was measured in accordance with the “Test methods fornonwovens” specified in JIS L 1913. The bending resistance was measuredfor each of the length direction (MID direction) and the width direction(CD direction) of a fibrous sheet.

[9] Stress S₀ (N/50 mm) at Initial Extension, Stress S₅ (N/50 mm) atExtension after Five Minutes, and Stress Relaxation Rate (%) in Examplesand Comparative Examples (Examples 1 to 4, Comparative Example 1)According to First Embodiment

A stress S₀ at initial extension as the stress at extension immediatelyafter extension in the length direction (MD direction) at 50% elongationand a stress S₅ at extension after five minutes as the stress atextension generated when the sheet was extended in the length direction(MD direction) at 50% elongation and held in this state for five minuteswere measured in accordance with the “Test methods for nonwovens”specified in JIS L 1913, and a stress relaxation rate was calculated inaccordance with the formula defined above.

[10] Stress at 50% Extension (N/50 mm) in Examples and ComparativeExamples (Examples 5 and 6, Comparative Examples 2 to 4) According toSecond Embodiment and Examples and Comparative Examples (Examples 7 and8, Comparative Examples 5 and 6) According to Third Embodiment

A basis weight was measured in accordance with the “Test methods fornonwovens” specified in JIS L 1913. The bending resistance was measuredfor each of the length direction (MD direction) and the width direction(CD direction) of a fibrous sheet. In Examples and Comparative Examples(Examples 5 and 6, Comparative Examples 2 to 4) according to the secondembodiment, a stress at 50% extension in the width direction (firstdirection, CD direction) of a fibrous sheet is represented by S₁, and astress at 50% extension in the length direction (second direction, MDdirection) is represented by S₂.

[11] Recovery Rate after 50% Extension

A tensile test in accordance with the “Test methods for nonwovens”specified in JIS L 1913 was carried out, and

a recovery rate after 50% extension was obtained based on the followingformula:

Recovery rate (%) after 50% extension=100−X.

In the formula, X represents a residual strain (%) after the tensiletest when load is removed immediately after the elongation rate hasreached 50% in the test. The recovery rates after 50% extension wasmeasured for each of the length direction (MD direction) and the widthdirection (CD direction) of a fibrous sheet.

[12] Compression Elastic Modulus Pe (%) in Examples and ComparativeExamples (Examples 5 and 6, Comparative Examples 2 to 4) According toSecond Embodiment and Examples and Comparative Examples (Examples 7 and8, Comparative Examples 5 and 6) According to Third Embodiment

A compression elastic modulus Pe was calculated based on the aboveformula [C] in accordance with the “Test methods for nonwovens”specified in JIS L 1913.

[13] Thickness Difference ΔT (mm) in Examples and Comparative Examples(Examples 5 and 6, Comparative Examples 2 to 4) According to SecondEmbodiment

A thickness difference ΔT was obtained as (T₁−T) in the above formula[C].

[14] Curved Surface Sliding Stress (N/50 mm)

First, a fibrous sheet was cut into a size of 50 mm in width and 600 mmin length so that the MD direction was the length direction, to obtain asample 1. Then, as shown in FIG. 1(a), one end of the sample 1 was fixedto a winding core 3 (a pipe roll formed of a polypropylene resin andhaving an outer diameter of 30 mm and a length of 150 mm) with asingle-sided adhesive tape 2. Then, with use of an alligator clip 4 (thegripping width was 50 mm, and a rubber sheet having a thickness of 0.5mm had been fixed on the inside of the clip with a double-sided adhesivetape before use), a weight 5 with 150 g was attached to the other end ofthe sample 1 to apply load to the whole width of the sample 1 evenly.

Then, while the winding core 3 to which the sample 1 was fixed waslifted up such that the sample 1 and the weight 5 were suspended, thewinding core 3 was rotated for five rounds so that the weight 5 did notsignificantly swing, to wind up the sample 1 and thus to lift up theweight 5 (see FIG. 1(b)). In this state, a contact between a cylindricalportion at an outermost peripheral portion of the sample 1 wrappedaround the winding core 3 and a planar portion of the sample 1 unwrappedaround the winding core 3 was defined as a base point 6 (the contact wasa border line between an area of the sample 1 wrapped around the windingcore 3 and an area of the sample 1 rendered vertical by the gravity ofthe weight 5), and the alligator clip 4 and the weight 5 were quietlyremoved so as not to move and shift the base point 6. Then, theoutermost peripheral portion of the sample 1 wound around the windingcore 3 was cut with a razor at a point 7 that was located a half-circleaway (180°) from the base point 6 along the sample 1, paying attentionto avoid cutting underlying the sample 1, to provide a cut 8 (see FIG.2).

A curved surface sliding stress between an outermost layer portion inthe sample 1 and an inner layer portion placed under the outermost layerportion (inner layer) and wrapped around the winding core 3 wasmeasured. For this measurement, a tensile tester (“Autograph”manufactured by Shimadzu Corporation) was used. The winding core 3 wasfixed on a jig 9 installed on a chuck base on a fixed side of thetensile tester (see FIG. 3), and the end of the sample 1 (the end towhich the alligator clip 4 had been attached) was gripped by a chuck 10on a load cell side to stretch the sample 1 at a tensile speed of 200mm/minute. When the sample 1 was removed (separated) at the cut 8, themeasured value (tensile strength) was regarded as the curved surfacesliding stress.

1. Production of Fibrous Sheet (First Embodiment) Example 1

As a latently crimpable fiber, a side-by-side type composite staplefiber [“Sofit PN780” manufactured by Kuraray Co., Ltd., 1.7 dtex×51 mmlong, number of machine crimps: 12 crimps/25 mm, number of crimps afterheat treatment at 130° C. for 1 minute: 62 crimps/25 mm] was preparedthat was constituted of a polyethylene terephthalate resin having anintrinsic viscosity of 0.65 [component (A)] and a modified polyethyleneterephthalate resin [component (B)] in which 20 mol % of isophthalicacid is copolmerized with 5 mol % of diethylene glycol. Using 100% bymass of this side-by-side type composite staple fiber, a carded webhaving a basis weight of 30 g/m² was provided by a carding method.

This carded web was moved on a conveyer net, and allowed to pass betweenthe conveyer net and a porous plate drum with pores (circular form)having a diameter of 2 mmφ and a pitch of 2 mm and being arranged in ahound's-tooth check pattern. From the inside of the porous plate drum, awater flow was injected in a spray form at 0.8 MPa toward the web andthe conveyer net, and thus an uneven distribution step for periodicallyforming a low-density region and a high-density region of fibers wasconducted.

Then, the carded web was transferred to a heating step while the web wasoverfed at about 200% without prevention of contraction in the heatingstep due to steam.

Then, the carded web was introduced to a steam injecting apparatusprovided in a belt conveyer, and steam at 0.5 MPa and a temperature ofabout 160° C. was ejected to the carded web perpendicularly from thesteam injecting apparatus to treat the web with steam, so thatcoil-shaped crimps of the latently crimped fibers were expressed, and atthe same time, the fibers were entangled. In this steam injectingapparatus, nozzles were installed in one of the conveyers so as to blowsteam toward the carded web through the conveyer belt. Each of the steaminjecting nozzles had a pore diameter of 0.3 mm, and an apparatus inwhich the nozzles were arranged in a line at a pitch of 2 mm in thewidth direction of the conveyer was used. The processing speed was 8.5m/min, and the distance between each nozzle and the conveyor belt on asuction side was 7.5 mm. Finally, the web was dried with hot air at 120°C. for 1 minute to obtain a stretchable fibrous sheet.

Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

Example 2

A stretchable fibrous sheet was produced in the same manner as inExample 1 except that the hot air drying temperature was set to 140° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction. In Examples 1 and 2and Comparative Example 1 to be described later, carded webs used hadthe same basis weight (30 g/m²).

Example 3

A commercially available polyurethane meltblown nonwoven fabric(“Meltblown UC0060” manufactured by Kuraray Kuraflex Co., Ltd.) wasthermally embossed and bonded at a treatment temperature of 130° C.,while being extended 1.5 times, onto one side of a commerciallyavailable polyester spunbond nonwoven fabric (“ecule 3201A” manufacturedby Toyobo Co., Ltd.) having a three-layer structure of spunbond nonwovenfiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiberlayer, and the resultant was subjected to gathering by relaxing theextension, so that a stretchable fibrous sheet was produced.

Example 4

A carded web having a basis weight of 30 g/m² was produced in the samemanner as in Example 1 except that 80% by mass of the latently crimpablefibers used in Example 1 and 20% by mass of heat-fusible fibers(“Sofista S220” manufactured by Kuraray Co., Ltd., 3.3 dtex×51 mm long)were used as fibers constituting a carded web, and a stretchable fibroussheet was produced in the same manner as in Example 1 except that thiscarded web was used.

Comparative Example 1

A stretchable fibrous sheet was produced in the same manner as inExample 1 except that the hot air drying temperature was set to 160° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

2. Evaluation of Fibrous Sheet (First Embodiment)

Each of the obtained fibrous sheets was subjected to the followingevaluation test.

(1) Seaming Feeling Evaluation Test

A fibrous sheet having a width of 2.5 cm was wrapped three times aroundthe second joint part of a forefinger while being stretched by 30%, andafter 5 minutes, the presence or absence of a color change of thefingertip was visually observed, and the presence or absence of pain atthe fingertip was confirmed.

(2) Wrapping Stability Evaluation Test

A fibrous sheet having a width of 2.5 cm was wrapped three times aroundthe second joint part of a forefinger while being stretched by 30%, andafter 5 minutes, the wearer bent and stretched the forefinger ten timesto check whether or not the fibrous sheet was loosened (shifted orpeeled).

TABLE 1 Comparative Example 1 Example 2 Example 3 Example 4 Example 1Number of average coil crimps (crimps/mm) 8.3 26.3 — 5.5 38.5 Averagecrimp pitch (μm) 120 38 — 181 26 Average curvature radius (μm) 62.8 52.5— 65.6 27.6 Basis weight (g/m²) 86.0 148.7 145.9 71.7 173.0 Thickness(mm) 1.13 1.35 1.70 0.95 1.39 Density (g/cm³) 0.08 0.11 0.09 0.08 0.12Breaking strength MD (N/50 mm) 13.5 22.8 59.7 34.5 30.5 CD (N/50 mm) 3.97.1 247.9 8.8 8.7 Elongation at break MD (%) 102 173 245 169 189 CD (%)108 150 14 101 181 Stress S₀ at initial MD (N/50 mm) 5.2 5.4 4.8 4.9 5.8extension Stress S₅ at extension after MD (N/50 mm) 4.1 4.4 4.0 2.7 5.3five minutes Stress relaxation rate (%) 78.8 81.5 83.3 55.1 91.4Recovery rate after 50% MD (%) 94.5 93.2 96.2 89.6 91.1 extension CD (%)91.8 91.5 — 83.5 82.6 Curved surface sliding (N/50 mm) 12.6 16.5 5.6 9.49.8 stress Evaluation Feeling of Presence or absence Absence AbsenceAbsence Absence Presence seaming of color change Presence or absenceAbsence Absence Absence Absence Presence of pain Wrapping Presence orabsence Absence Absence Absence Presence Absence stability of loosening

3. Production of Fibrous Sheet (Second Embodiment) Example 5

As a latently crimpable fiber, a side-by-side type composite staplefiber [“Sofit PN780” manufactured by Kuraray Co., Ltd., 1.7 dtex×51 mmlong, number of machine crimps: 12 crimps/25 mm, number of crimps afterheat treatment at 130° C. for 1 minute: 62 crimps/25 mm] was preparedthat was constituted of a polyethylene terephthalate resin having anintrinsic viscosity of 0.65 [component (A)] and a modified polyethyleneterephthalate resin [component (B)] in which 20 mol % of isophthalicacid is copolmerized with 5 mol % of diethylene glycol. Using 100% bymass of this side-by-side type composite staple fiber, a carded webhaving a basis weight of 30 g/m² was provided by a carding method.

This carded web was moved on a conveyer net, and allowed to pass betweenthe conveyer net and a porous plate drum with pores (circular form)having a diameter of 2 mmφ and a pitch of 2 mm and being arranged in ahound's-tooth check pattern. From the inside of the porous plate drum, awater flow was injected in a spray form at 0.8 MPa toward the web andthe conveyer net, and thus an uneven distribution step for periodicallyforming a low-density region and a high-density region of fibers wasconducted.

Then, the carded web was transferred to a heating step while the web wasoverfed at about 200% without prevention of contraction in the heatingstep due to steam.

Then, the carded web was introduced to a steam injecting apparatusprovided in a belt conveyer, and steam at 0.5 MPa and a temperature ofabout 160° C. was ejected to the carded web perpendicularly from thesteam injecting apparatus to treat the web with steam, so thatcoil-shaped crimps of the latently crimped fibers were expressed, and atthe same time, the fibers were entangled. In this steam injectingapparatus, nozzles were installed in one of the conveyers so as to blowsteam toward the carded web through the conveyer belt. Each of the steaminjecting nozzles had a pore diameter of 0.3 mm, and an apparatus inwhich the nozzles were arranged in a line at a pitch of 2 mm in thewidth direction of the conveyer was used. The processing speed was 8.5m/min, and the distance between each nozzle and the conveyor belt on asuction side was 7.5 mm. Finally, the web was dried with hot air at 120°C. for 1 minute to obtain a stretchable fibrous sheet.

Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

Example 6

A stretchable fibrous sheet was produced in the same manner as inExample 5 except that the hot air drying temperature was set to 140° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction. In Examples 5 and 6and Comparative Example 2 to be described later, carded webs used hadthe same basis weight (30 g/m²).

Comparative Example 2

A stretchable fibrous sheet was produced in the same manner as inExample 5 except that the hot air drying temperature was set to 160° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

Comparative Example 3

A carded web having a basis weight of 30 g/m² was produced in the samemanner as in Example 5 except that 80% by mass of the latently crimpablefibers used in Example 5 and 20% by mass of heat-fusible fibers(“Sofista S220” manufactured by Kuraray Co., Ltd., 3.3 dtex×51 mm long)were used as fibers constituting a carded web, and a stretchable fibroussheet was produced in the same manner as in Example 5 except that thiscarded web was used.

Comparative Example 4

A commercially available polyurethane meltblown nonwoven fabric(“Meltblown UC0060” manufactured by Kuraray Kuraflex Co., Ltd.) wasthermally embossed and bonded at a treatment temperature of 130° C.,while being extended 1.5 times, onto one side of a commerciallyavailable polyester spunbond nonwoven fabric (“ecule 3201A” manufacturedby Toyobo Co., Ltd.) having a three-layer structure of spunbond nonwovenfiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiberlayer, and the resultant was subjected to gathering by relaxing theextension, so that a stretchable fibrous sheet was produced.

4. Evaluation of Fibrous Sheet (Second Embodiment)

Each of the obtained fibrous sheets was subjected to the followingevaluation test.

(Ease of Bending of Joint Part after Wrapping Fibrous Sheet)

A fibrous sheet having a width of 5 cm was wrapped three times aroundthe second joint part of a forefinger while being stretched by 30%, andwhen the second joint part was bent, tightness applied to the finger andhardness were evaluated with the following five scores, and an averagescore of five subjects was obtained. In Comparative Examples 2 to 4,especially Comparative Example 4, when the wearer bent the second jointpart, the fibrous sheet was folded into a wrinkle shape (wavy shape) onthe inside of the joint part, and it seemed that the joint part wasdifficult to be bent in appearance.

Score 5: No tightness or hardness was sensed.

Score 4: Little tightness or hardness was sensed.

Score 3: Slight tightness or hardness was sensed.

Score 2: Strong tightness or hardness was sensed.

Score 1: Extremely strong tightness or hardness was sensed.

TABLE 2 Comparative Comparative Comparative Example 5 Example 6 Example2 Example 3 Example 4 Number of average coil crimps (crimps/mm) 8.1 27.97.1 36.6 — Average crimp pitch (μm) 123 36 141 27 — Average curvatureradius (μm) 62.7 53.3 61.3 28.1 — Basis weight (g/m²) 91.4 150.3 71.7172.1 165.8 Thickness T₁ (mm) 1.15 1.32 0.95 1.33 1.56 T₃ (mm) 2.76 3.232.53 3.51 4.36 {T₃/(3 × T₁)} × 100 (%) 80.0 81.6 88.8 88.0 93.2 Density(g/cm³) 0.08 0.11 0.08 0.13 0.11 Breaking strength MD (N/50 mm) 14.723.7 34.5 30.3 74.2 CD (N/50 mm) 4.2 6.7 8.8 8.9 301.8 Elongation atbreak MD (%) 105 165 169 177 362 CD (%) 103 155 101 165 15 Stress at S₁(N/50 mm) 1.19 1.38 5.9 4.13 — 50% S₂ (N/50 mm) 5.21 5.39 4.7 8.51 4.79extension S₂/S₁ — 4.4 3.9 0.8 2.1 — Recovery rate after 50% MD (%) 95.494.2 90.5 88.9 96.8 extension CD (%) 94.6 92.1 81.6 84.2 — Compressionelastic (%) 76.2 81.1 89.5 87.9 86.5 modulus Pe Thickness difference ΔT(mm) 0.4 0.4 0.3 0.3 0.5 Curved surface sliding stress (N/50 mm) 12.317.4 9.3 19.8 0.5 Evaluation Ease of Average score 4.2 4.0 2.4 2.0 1.6bending

5. Production of Fibrous Sheet (Third Embodiment) Example 7

As a latently crimpable fiber, a side-by-side type composite staplefiber [“Sofit PN780” manufactured by Kuraray Co., Ltd., 1.7 dtex×51 mmlong, number of machine crimps: 12 crimps/25 mm, number of crimps afterheat treatment at 130° C. for 1 minute: 62 crimps/25 mm] was preparedthat was constituted of a polyethylene terephthalate resin having anintrinsic viscosity of 0.65 [component (A)] and a modified polyethyleneterephthalate resin [component (B)] in which 20 mol % of isophthalicacid is copolmerized with 5 mol % of diethylene glycol. Using 100% bymass of this side-by-side type composite staple fiber, a carded webhaving a basis weight of 30 g/m² was provided by a carding method.

This carded web was moved on a conveyer net, and allowed to pass betweenthe conveyer net and a porous plate drum with pores (circular form)having a diameter of 2 mmφ and a pitch of 2 mm and being arranged in ahound's-tooth check pattern. From the inside of the porous plate drum, awater flow was injected in a spray form at 0.8 MPa toward the web andthe conveyer net, and thus an uneven distribution step for periodicallyforming a low-density region and a high-density region of fibers wasconducted.

Then, the carded web was transferred to a heating step while the web wasoverfed at about 200% without prevention of contraction in the heatingstep due to steam.

Then, the carded web was introduced to a steam injecting apparatusprovided in a belt conveyer, and steam at 0.5 MPa and a temperature ofabout 160° C. was ejected to the carded web perpendicularly from thesteam injecting apparatus to treat the web with steam, so thatcoil-shaped crimps of the latently crimped fibers were expressed, and atthe same time, the fibers were entangled. In this steam injectingapparatus, nozzles were installed in one of the conveyers so as to blowsteam toward the carded web through the conveyer belt. Each of the steaminjecting nozzles had a pore diameter of 0.3 mm, and an apparatus inwhich the nozzles were arranged in a line at a pitch of 2 mm in thewidth direction of the conveyer was used. The processing speed was 8.5m/min, and the distance between each nozzle and the conveyor belt on asuction side was 7.5 mm. Finally, the web was dried with hot air at 120°C. for 1 minute to obtain a stretchable fibrous sheet.

Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

Example 8

A stretchable fibrous sheet was produced in the same manner as inExample 7 except that the hot air drying temperature was set to 140° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction. In Examples 7 and 8and Comparative Example 5 to be described later, carded webs used hadthe same basis weight (30 g/m²).

Comparative Example 5

A stretchable fibrous sheet was produced in the same manner as inExample 7 except that the hot air drying temperature was set to 160° C.Observation of a surface and cross section in the thickness direction ofthe obtained fibrous sheet under an electron microscope (100magnifications) revealed that fibers were oriented substantiallyparallel with the plane direction of the fibrous sheet, and crimpedsubstantially uniformly in the thickness direction.

Comparative Example 6

A commercially available polyurethane meltblown nonwoven fabric(“Meltblown UC0060” manufactured by Kuraray Kuraflex Co., Ltd.) wasthermally embossed and bonded at a treatment temperature of 130° C.,while being extended 1.5 times, onto one side of a commerciallyavailable polyester spunbond nonwoven fabric (“ecule 3201A” manufacturedby Toyobo Co., Ltd.) having a three-layer structure of spunbond nonwovenfiber layer/meltblown nonwoven fiber layer/spunbond nonwoven fiberlayer, and the resultant was subjected to gathering by relaxing theextension, so that a stretchable fibrous sheet was produced.

6. Evaluation of Fibrous Sheet (Third Embodiment)

Each of the obtained fibrous sheets was subjected to the followingevaluation test.

(Concavo-Convex Fitting Property)

A fibrous sheet having a width of 5 cm was wrapped three times around aforefinger, a wrist, and an ankle while being stretched by 30%, and thefitting property for the shape of surface protrusions and recesses ofthe joint parts of these sites was evaluated with the following fivescores, and an average score of five subjects was obtained.

Score 5: No floating of fibrous sheet was sensed at all convavoportions.

Score 4: Little floating of fibrous sheet was sensed.

Score 3: Slight floating of fibrous sheet was sensed.

Score 2: High degree of floating of fibrous sheet was sensed.

Score 1: Extremely high degree of floating of fibrous sheet was sensed.

TABLE 3 Comparative Comparative Example 7 Example 8 Example 5 Example 6Number of average coil crimps (crimps/mm) 8.4 25.8 37.9 — Average crimppitch (μm) 119 39 26 — Average curvature radius (μm) 67.8 55.1 27.7 —Basis weight (g/m²) 91.0 138.4 182.3 165.8 Thickness (mm) 1.21 1.35 1.371.56 Density (g/cm³) 0.08 0.10 0.13 0.11 Bending resistance MD (mN/200mm) 91 175 237 115 CD (mN/200 mm) 148 266 434 847 Breaking strength MD(N/50 mm) 15.6 21.8 30.7 74.2 CD (N/50 mm) 4.3 6.5 9.1 301.8 Elongationat break MD (%) 106 159 191 362 CD (%) 105 145 161 15 Stress at 50%extension MD (N/50 mm) 5.17 4.33 5.62 2.1 CD (N/50 mm) 3.03 3.14 3.83 —Recovery rate after 50% MD (%) 95.6 94.6 88.2 96.7 extension CD (%) 91.691.3 82.6 — Compression elastic modulus Pe (%) 71.1 81.5 87.1 87.5Curved surface sliding stress (N/50 mm) 13.3 18.9 21.1 0.4 EvaluationConcavo-convex Average score 4.4 4.1 2.8 1.8 fitting property[Forefinger] Average score 4.6 4.0 2.7 2.2 [Wrist] Average score 4.2 4.22.9 2.4 [Ankle]

REFERENCE SIGNS LIST

1: Sample, 2: Single-sided adhesive tape, 3: winding core, 4: Alligatorclip, 5: Weight, 6: Base point, 7: Point located half-circle away frombase point, 8: Cut, 9: Jig, 10: Chuck

1. A fibrous sheet having a stress relaxation rate defined by a formulabelow of less than or equal to 85%:stress relaxation rate [%]=(stress S ₅ at extension after fiveminutes/stress S ₀ at initial extension)×100 when a stress at extensionimmediately after extension in an in-plane first direction at 50%elongation is defined as a stress S₀ (N/50 mm) at initial extension, anda stress at extension at a time of extending in the first direction at50% elongation for five minutes is defined as a stress S₅ (N/50 mm) atextension after five minutes.
 2. The fibrous sheet according to claim 1,wherein the stress relaxation rate is greater than or equal to 65%. 3.The fibrous sheet according to claim 1, wherein the stress S₀ at initialextension is from 2 to 30 N/50 mm.
 4. The fibrous sheet according toclaim 1, wherein the fibrous sheet has a length direction and a widthdirection, and the first direction is the length direction.
 5. A fibroussheet that satisfies a formula below:{T ₃/(3×T ₁)}×100≤85[%] when a thickness of a single fibrous sheetmeasured in accordance with A method specified in JIS L 1913 is definedas T₁ [mm], and a thickness of three superimposed sheets measured underthe same conditions is defined as T₃ [mm].
 6. The fibrous sheetaccording to claim 5, wherein the fibrous sheet satisfies a formulabelow:S ₂ /S ₁≥3 when a stress at extension at a time of extension in anin-plane first direction at 50% elongation is defined as a stress S₁(N/50 mm) at 50% extension, and a stress at extension at a time ofextension in an in-plane second direction orthogonal to the firstdirection at 50% elongation is defined as a stress S₂ (N/50 mm) at 50%extension.
 7. The fibrous sheet according to claim 6, wherein thefibrous sheet has a length direction and a width direction, and thefirst direction is the width direction.
 8. The fibrous sheet accordingto claim 5, wherein the fibrous sheet has a basis weight of greater thanor equal to 50 g/m².
 9. The fibrous sheet according to claim 5, whereinthe fibrous sheet has a compression elastic modulus measured inaccordance with JIS L 1913 of less than or equal to 85%.
 10. A fibroussheet having a length direction and a width direction, wherein a bendingresistance in the width direction measured in accordance withHandle-o-Meter method specified in JIS L 1913 is less than or equal to300 mN/50 mm.
 11. The fibrous sheet according to claim 10, wherein thebending resistance in the width direction is lower than a bendingresistance in the length direction.
 12. The fibrous sheet according toclaim 10, wherein the fibrous sheet has a compression elastic modulusmeasured in accordance with JIS L 1913 of less than or equal to 85%. 13.The fibrous sheet according to claim 10, wherein the fibrous sheet is anonwoven fabric sheet, and fibers constituting the nonwoven fabric sheethave an average fineness of less than or equal to 20 dtex.
 14. Thefibrous sheet according to claim 1, wherein the fibrous sheet is anonwoven fabric sheet.
 15. The fibrous sheet according to claim 14,wherein the fibrous sheet comprises crimped fibers.
 16. The fibroussheet according to claim 1, wherein the fibrous sheet has a curvedsurface sliding stress of 3 to 30 N/50 mm.
 17. The fibrous sheetaccording to claim 1, wherein the fibrous sheet is a bandage.
 18. Thefibrous sheet according to claim 5, wherein the fibrous sheet is anonwoven fabric sheet.
 19. The fibrous sheet according to claim 18,wherein the fibrous sheet comprises crimped fibers.
 20. The fibroussheet according to claim 10, wherein the fibrous sheet is a nonwovenfabric sheet.
 21. The fibrous sheet according to claim 20, wherein thefibrous sheet comprises crimped fibers.
 22. The fibrous sheet accordingto claim 5, wherein the fibrous sheet has a curved surface slidingstress of 3 to 30 N/50 mm.
 23. The fibrous sheet according to claim 10,wherein the fibrous sheet has a curved surface sliding stress of 3 to 30N/50 mm.
 24. The fibrous sheet according to claim 5, wherein the fibroussheet is a bandage.
 25. The fibrous sheet according to claim 10, whereinthe fibrous sheet is a bandage.